You correct as you go along. It's not like you suddenly wake up and don't do it anymore; it's like doing a math paper and having a bunch of mistakes which you fix. By fixing them you learn to understand the problems better and make fewer mistakes the next time, fix those, and continue. The more complex or difficult the problem the more likely one is to make a mistake of some sort when working on it. It's not bad to make mistakes, that's how we learn!