You don't really want to waste your time trying to understand why you made a choice. If you're like me and like learning through trial and error, then try to think of it this way. When you are trying to choose between several different methods to learn something, you're probably going to pick the most efficient method that you could understand. If you've decided to study with "free" study tools or a free textbook, then you're probably going to pick the one that you have the least knowledge about.