I'm in the rather odd situation of not knowing what I wanted to become. I thought I wanted to become a lawyer, then I thought I wanted to become a teacher. Now I realise I don't know what I wanted to do, I was probably really depressed in my teens, and I think that was reflected in the work I did at college/uni. Not that I didn't do well, I just coasted through for the sake of doing it.
Now I still don't know what I want to do, but at least I know I don't know what I want to do.