My twenties started 6 months ago, but I've already discovered several of these. I discovered that despite knowing several languages and frameworks, i can't actually program. Despite being able to get descent grades in high-school without studying i can't do it with university material, so i have less time to play with computers, because i actually have to put in effort. I thought smoking is bad for you, the same way…
A lot of people underestimate what higher education teaches you. You may be able to learn how to program by yourself, but you don't learn how to do the boring hard work.