This is why I don't like self-study for mathematics. A lot of the stuff is very simple once you understand what it's for, but finding out what it's for from the

This is why I don't like self-study for mathematics. A lot of the stuff is very simple once you understand what it's for, but finding out what it's for from the formal definition is an uphill battle. And then, after you see the thing for what it is (months later), you start coming up with questions that lead to more formalism. Studying from an encyclopaedia is hard, and even a good book will only get you as far as well-known results. Answers are much easier to learn from, so you want someone to provide you with the correct questions and avoid the difficult ones.