Great Work
When you’re implementing a bad plan yourself, instead of having a mentor bail you out by fixing it, a few really useful things happen:
- You learn many more details about why it was a bad idea. If someone else tells you your plan is bad, they’ll probably list the top two or three reasons. By actually following through, you’ll also get to learn reasons
Learning to Build Conviction
Overall, I probably did a pretty bad job. But, importantly, I was able to see my mistakes play out in the real world. Instead of modeling what other people would tell me to do, I built a model of the problem directly. So when I got negative feedback, it wasn’t “Mentor X thinks this plan is bad” but “the world works differently than you expected.”
Learning to Build Conviction
Because the stakes are higher and it takes longer to see the results, all these decisions require what I’d call conviction : the confidence that your idea is good enough that it’s worth throwing a lot of effort behind.
Learning to Build Conviction
"I'm actually not that good at Git!" — a funny line from someone who wrote the book on it, but he continues. "I just understand what it's like to not understand something, and what it's like to get over that. I have a drive to understand how it works at a fundamental level so I can teach people."
A GitHub Co-founder's Next Commit | Open Source Pledge

Do you think the only time musicians play their instruments is when they are on stage? Do you think the only time that batters hit balls is during games? Do you think the only time lawyers give a closing is at trial? Of course not. These people are professionals; and professionals practice! Professionals study the minutia of their disciplines.... See more
Clean Coder Blog
At its best, starting a startup is merely an ulterior motive for curiosity. And you'll do it best if you introduce the ulterior motive toward the end of the process.
So here is the ultimate advice for young would-be startup founders, boiled down to two words: just learn.
So here is the ultimate advice for young would-be startup founders, boiled down to two words: just learn.
Starting a startup will change you a lot. So what you're trying to estimate is not just what you are, but what you could grow into, and who can do that?