Some may be born with the fundemental building blocks necessary to develop "IT" but I don't think that it's completely hereditary. Say for instance a kid is born with the genetic predisposition to defy authority, to buck the trend, break rules, be his own person at any cost. This kid has an extremely authoritarian father, who tries to break his son of what he considers to be a wild and irresponsible demeanor. Growing up under that kind of conflict, with that kind of stress does two things, galvanizes the kids belief that he's on his own and if he's going to "make it" he's got to be true to himself, but it also makes him realize that some things are worth fighting for and others will eventually lead to consequences no amount of will power will shield him from.
He grows up into a will to win individual with strong character and a lean on me attitude, but at the same time understands when that's not enough to pull through. He's still one sided, but not out of control.
Take a kid born with the same genetic dispositions who grows up with a single mother who lets him do whatever he wants, no discipline, no consequences, and he ends up in prison rather than a college football team.
Does that make any sense?