Paul Graham:

Having gotten it down to 13 sentences, I asked myself which I’d choose if I could only keep one.

Understand your users. That’s the key. The essential task in a startup is to create wealth; the dimension of wealth you have most control over is how much you improve users’ lives; and the hardest part of that is knowing what to make for them. Once you know what to make, it’s mere effort to make it, and most decent hackers are capable of that.

Understanding your users is part of half the principles in this list. That’s the reason to launch early, to understand your users. Evolving your idea is the embodiment of understanding your users. Understanding your users well will tend to push you toward making something that makes a few people deeply happy. The most important reason for having surprisingly good customer service is that it helps you understand your users. And understanding your users will even ensure your morale, because when everything else is collapsing around you, having just ten users who love you will keep you going.

Also::

It’s better, initially, to make a small number of users really love you than a large number kind of like you.

Paul Graham:

Merely measuring something has an uncanny tendency to improve it. If you want to make your user numbers go up, put a big piece of paper on your wall and every day plot the number of users. You’ll be delighted when it goes up and disappointed when it goes down. Pretty soon you’ll start noticing what makes the number go up, and you’ll start to do more of that. Corollary: be careful what you measure.

Paul Graham:

Because biographies of famous scientists tend to edit out their mistakes, we underestimate the degree of risk they were willing to take. And because anything a famous scientist did that wasn’t a mistake has probably now become the conventional wisdom, those choices don’t seem risky either.

Biographies of Newton, for example, understandably focus more on physics than alchemy or theology. The impression we get is that his unerring judgment led him straight to truths no one else had noticed. How to explain all the time he spent on alchemy and theology? Well, smart people are often kind of crazy.

But maybe there is a simpler explanation. Maybe the smartness and the craziness were not as separate as we think. Physics seems to us a promising thing to work on, and alchemy and theology obvious wastes of time. But that’s because we know how things turned out. In Newton’s day the three problems seemed roughly equally promising. No one knew yet what the payoff would be for inventing what we now call physics; if they had, more people would have been working on it. And alchemy and theology were still then in the category Marc Andreessen would describe as “huge, if true.”

Newton made three bets. One of them worked. But they were all risky.