Would you say it's lack of talent/intelligence? Discipline to study? Lack of a bankroll and any ability to reliably build one? Lack of good games? Social considerations? Ability to remove emotion from one's game?

I know that, for me, the tilt factor was always my biggest weakness. Everything else was easy, but the fact that I could so often lose even when I had an edge definitely provoked me into making some stupid plays when I started out, and I definitely spewed money I didn't have to. If I hadn't been working a high paying job as well, I might well have gone busto.