If you're reading this, you should read Muscle, by Samuel Wilson Fussell, because it's about a topic that can't be taught, only recognized and cultivated: obsession. Obsession propels people past skill and into mastery, it's the thing that moves from "good" into "top". Don't think I quite have it, myself, right now, though maybe I did, at one point. It's the thing you do for no reason, however many "reasons" you come up with, the thing that keeps you moving. Why'd Sam get obsessed? He thinks '80s New York streets scared him, and that could be a small part, but it sounds like an excuse. The muscle thing could be a rebellion against his parents, he implies. Could be some third thing, I'd say, and the truth is probably tautological, it got him cause it got him.