On Execution

This page was not made to persuade anyone. If you are reading it, you most likely arrived here through someone's introduction. So this is not a polished recruiting post. It is closer to a letter, written to find people who believe the same thing — or who want to try believing it. If you read to the end and think, this is about me, then we should meet. If not, please feel free to walk away.

Some of you may scoff and wonder what this nonsense is. That is fine. This letter was never meant for everyone.

First, I should tell you my story

In 2011, I started a company at a time when I barely understood what I was doing. I had my own conviction, but nowhere near the skill to carry it. As a result, I burned a great deal of time in a painfully inefficient way.

There was a service called "Ulabla," the first thing I built together with Seunggun Lee. Holding the belief that "true relationships are formed more meaningfully offline than online," we offered what we believed was right in a way the world did not want. People wanted an expanded social media that let them reach and be reached by more people — they had no interest in a service for separately managing offline gatherings.

And yet we did not stop. We polished the UX further, tuned performance so the app would run on a local database when the network dropped and sync back when it reconnected, and even filed a patent for an authentication method using ultrasonic communication. We carried more conviction than the situation deserved, without communicating enough with reality — the market and the customers — and even when we did, we kept executing without properly reflecting on or learning from the results.

We spent more than a year that way, learning almost nothing meaningful about the market or the customers. The next product, a voting solution called Davote, drew a bigger response, but it was not the size of impact we wanted — and honestly, it was not so different.

I do not regret that experience at all. I believe it was because of it that, when the next opportunity called Toss came, we were able to make the most of it.

Two things I learned too late

Years later, around the time Toss had found its footing, a thought struck me. Nothing I had learned from those failures was wasted — but did it really have to cost that much time and money to learn it? If I were to do it again, I would never do it so inefficiently. At the very least, I hoped that founders better than me would not wander the same road, so they could change the world faster.

Looking back, there are two things I should have learned much earlier.

One: I spent conviction on what needed to be verified.

It is not that the problem I wanted to solve was wrong (it may have been), but that I treated the belief as a premise rather than a hypothesis. We never sought answers to the questions that actually mattered. Do customers feel the problem I see as a problem? Does our solution solve it in the way customers want? Before ever confirming those answers, we were so sure of our own answer that we spent over a year refining design, performance, and patents. It all felt like progress, but in truth it was sophistication built on unverified demand. Making a service smooth is tangible, controllable, and never rejects you. That is why it is the easiest fake progress to fall into.

Two: I received the world's signals and still failed to learn.

This one is scarier, and far harder to judge. If the first mistake was not checking for real signals, the second was receiving them and hearing only what I wanted to hear. The stronger your conviction, the more your brain files refutation as noise and agreement as signal.

Besides, if you build something, someone will always use it. The problem was that we could not tell whether that small response was a current that would grow into the change we wanted, or just a handful of users whose existence reassured us. We looked at the data but failed to judge from it — and so we never coldly asked whether the change we were building was really the change we wanted.

Put these two together and they come to one thing. We spun the wheel hard, but the wheel touched nothing. We truly worked hard. We spun that wheel so hard that even now I doubt I could spin it harder. You, reading this, will surely work hard too. Which is why what matters more is how you work hard.

So I came to see execution differently

We commonly believe that thinking more and planning more precisely will yield better answers. Where the destination and the route are clear, that is mostly true. And most of us have been drilled in this kind of thinking for so long, through years of schooling, that we do it well without much effort.

But in domains of high uncertainty, the story changes. A startup founder is someone who stands in the middle of countless uncertainties and creates new value out of their own belief. So a founder's execution must be the act of illuminating those uncertainties, one by one. Imagine this. It is a pitch-black night, and you must cross a river. There are stepping stones somewhere, but you cannot see them. A founder is someone who has already seen the world waiting on the other side of this river. How could they have seen it without ever crossing? That seeing is conviction — a story we will return to later. Now, we have to cross by dipping a foot in, little by little, to find out whether this spot is stone or water. Do not forget: it is pitch black. Stone or water — you only know by dipping your foot in. Taking that first step, could any amount of deep thought and planning guarantee it lands right? Of course, in reality you are never quite this starved of information, but once you are in it, I think you will agree it is not so different.

A startup is an organization that deals in this kind of uncertainty. New markets, new customers, new solutions. In such territory, more thinking and more elaborate planning amount to spinning fantasies out of information that does not yet exist. The information we need is always on the other side of execution. That is why an 80-point execution, paradoxically, lets us learn faster than a 100-point plan. Execution is not an inferior substitute for planning — it is the only tool that produces the data planning needs.

Do not misunderstand: 80 points does not mean lowering your standards. Things usually look unfinished; you want to prepare more and build it better. You want to make it a 100. Say the 80-point version takes one day and the 100-point version takes seven. But we do not yet know whether this execution means anything in the real world at all. In that situation, the version that feels like an 80 is actually the 100-point choice. Filling in the last 20 points before the direction is confirmed can be — as when I kept polishing our UX — polishing the wrong spot to a shine. Stopping at 80 is not laziness. It is the discipline of cutting off, by force of will, the comfort that refining gives you. That is why it is harder than perfectionism.

But speed alone is not enough. In execution, density matters as much as speed.

Time is the most expensive resource a founder has. Let time slip away and you burn that much more of your people and your money — and above all, you may miss the window of opportunity while it is open. So within the same stretch of time, we must attempt as much as possible and learn as much as possible from every attempt.

Attempting a lot does not mean spraying bullets in every direction like Rambo. Nor does it mean lying prone all day for a single shot like a sniper. Aim and fire — of the two, the aiming must be there. However brief, knowing what this one shot is meant to confirm before you pull the trigger, then checking whether it hit or missed. Learning bit by bit through that repetition. This is what I call raising the density of execution.

So the right execution is not execution done impressively. It is execution that teaches you something about the problem you are solving, the market, and the customer. Execution that clears away one uncertainty with every shot. Don't just execute. Execute with density.

And on what it means to know

Can you learn to ride a bicycle from a book? Words barely help; a video is a little better; but nothing is as sure as actually riding. Fall a few times, and a sense that no writing could explain settles into your body.

The failures I described above are easy for anyone to understand on paper. Do not build sophistication on unverified demand; do not hear only the signals you want to hear. You nod along. But unless it is connected to your own business, your own customers, your own data, it is not knowledge — merely information. For information to become real knowledge, you and it must be joined by countless capillaries. And that connection forms only through direct execution. Only when it becomes truly connected to you does it finally become knowing.

Learning anything in life mostly works this way, and business is no exception. What matters more — and is harder — is not the propositional knowledge that fits into books, but the knowledge that enters only through doing.

And it does not end there. Even after you truly know, you now have to actually do it — in your own life, in your own business. But we do not always do what we are capable of doing. We know we should eat well and exercise for our health, and we could, yet most of us do not live that way. Set good hypotheses, execute them, analyze the results coldly — no founder is unaware of this. And yet, amid pressure, fear, and the mess of real situations, the person who does it every single time is rare.

This distance between knowing and doing does not close by knowing more. It closes only through repeated execution. So this is not a problem of learning; it is a problem of training. This is why practice is necessary.

Yet this training is unusually hard to do alone. The stronger your conviction, the harder it is to see where your own aim is off. Whether you just aimed and fired, or fled once again to what is familiar — when someone beside you can point that out, and hold you back one more time at the moment you want to run, the density of the training changes completely. It is the same reason athletes have coaches.

So this is what I believe. Learn it with your real business, by actually doing it. But because it must be done very consciously — not just done — you will do it better with someone beside you who draws your capacity out to its fullest.

That is why I started the Practice program.

Why the earliest stage, of all times

Because this training builds fundamental fitness.

Track and field has many events. The explosive sprint, the enduring marathon, hurdles cleared on rhythm, the long jump thrown with the whole body. The specific skills each event demands are completely different. But all of those skills grow on the same foundation: endurance and strength. If your base fitness is shallow, you hit your limits quickly no matter which event you choose.

Founding a company is no different. The capabilities you need vary with the business, but beneath them lies a common foundation: the ability to form a hypothesis, execute it, and learn from the result. This capacity to learn is a founder's fundamental fitness. And the early days — when so much is still undecided and the possibilities are boundless — are the best time to build it.

What's more, in the early days, whether things go well or badly, an enormous amount of data pours into you and your team. The problem is that this data does not turn into learning by itself. As happened to me, if you see the data but fail to learn from it, it simply flows away. There is no time like the beginning to engrave the habit of turning that flood of data into real learning. The loop that hardens in this period will shape the years that follow.

To be honest, doing this well does not guarantee success. There is clearly a part of success that skill alone cannot explain. But this much I believe: if luck ever comes our way, this well-trained fitness will let us ride that wave faster and farther. And since it is on this foundation that each of us must eventually pave our own road and design our own way, there is no better time than the beginning to lay it.

And before it is logic, this is also simply my heart. Rather than sharing in the success of a great company, I want to share in a beginning where nothing has been proven yet. I want to be the one who believes first, when no one else does — and I hope that belief lets more people dare to try. As it was at the start of Toss, there is a season that is darkest and yet holds the most open doors. I want to be someone who shares that season.

So: PRAX Practice

If you have read this far, I think what I believe has already come through.

Change does not happen by thinking longer or thinking more. Only when action collides with reality does real change happen — in you and in the world. I gave this belief the name PRAX. PRAX is a spirit before it is a program. For anyone who wants to make real change in themselves and the world, it is one path to reach that change.

The name PRAX comes from Praxis. In ancient Greece, praxis was the counterpart of theory (theoria) — practice that is completed not by knowing in the head but by doing. Aristotle believed that a good life is built not on knowledge but on the repetition of practice. That is exactly the story we have been sharing. And so, Prax is Praxis.

And Practice is the first experiment in applying this way of living to the field of company building. Like you, I too am beginning a challenge — to reach what I want through execution, through this experiment.

Practice is not a lecture. It is not mentoring, and it is not a book club.

The answer is always on the other side of execution. And the distance between knowing and doing can be closed through repeated discipline. Practice is the first attempt to turn that repetition into a founder's actual weekly loop.

As I said earlier, the early days pour an enormous amount of input on you. Only when you grow while bearing it does luck become yours. For that, you need a solid execution loop. In Toss's early days, it was the sprint of Scrum. But the form does not matter. What matters is whether a dense cycle of hypothesis, execution, and learning is turning.

That density is ultimately a standard, and the standard is set by the founder's tenacity and experience. To be honest, tenacity is beyond my reach — that, you must bring. But experience is different. Setting a minimum standard through the experience of executing together, and building the foundation on which you will correctly learn from the countless inputs you are about to face — that is something I can help with. So Practice is not a place to discuss the market or the business you already know better than anyone. It is a place to grind, together, the fundamental fitness beneath it: a solid execution loop.

We will spend the next five weeks together. You will choose your single most important hypothesis, and we will turn the loop once every week.

The first week sets the direction. You refine your mission from your conviction and define the core hypothesis to verify first. From the second week to the fifth, for four weeks, we turn one Action Loop of hypothesis, execution, and learning each week. This loop is not a unit of work; it is a unit of learning. Twice a week, 90 minutes each: once, you and I go deep, one on one, into your hypothesis and execution; once, all participants gather to reflect on one another's week. And between the sessions, you collide with reality.

When the five weeks end, I hope two things remain. A self that is sturdier than five weeks before, and a high-density execution loop you can keep turning on your own after the program ends.

This is my hope. That when you meet your luck, you grow more fully. That the time it takes to reach what you intend is shortened, even a little. That a better world arrives, even slightly sooner. That is the contribution I hope to make, however small — and the work I want to do.

To you

Is there a world you want to change? Do you want that change to happen not as a picture in your head, but in reality, for real? And to make it so, are you ready — before anything else — to sharpen yourself?

Then we should meet.

These five weeks will not be comfortable. There will be more time spent facing reality squarely than receiving warm consolation. But for someone who truly wants to grow, I believe you already know that this facing is a far greater gift than consolation.

If you have a business that has already touched reality, and you are the founder who decides its direction, apply below. The size of the business does not matter. There is no participation fee. Bring that readiness instead.

I will read every application myself, one by one.