Fighting comes down to who you are as a person. With B.J. Penn, he has no problems, not a hard upbringing and came up with money or whatever and he's just a fighter, he enjoys the fight and he refined his skills so I don't think it necessarily has to be a rough upbringing for guys to be great fighters.
Win or lose or draw, you always go back and critique your performance and say you could have done things better. Even if I put the guy away in one round, I can go back and say I made a lot of mistakes and need to tighten up. But that's the type of person I am. Improve. Improve. Improve. When I lose I come back stronger than ever.