Don't buy this 'believe in yourself' rubbish. Why do they keep telling youngsters that? There's no point believing in yourself if you don't know what you're doing. Once you've got a vision of what you want to do, by all means stick to that passionately and doggedly. Believe in your ideas. It's not quite the same thing.
I got thrown out of music school for even listening to Fats Domino and Ray Charles. I was asked, 'What kind of music do you like to listen to?' and I said, 'Well, I do like Paul Hindemith and Igor Stravinsky but I also like Fats Domino and Ray Charles,' and they literally said, 'Either forget about that or leave.'