I can't fistfight for shit, I'm not strong, etc...
But I'm psycho and determined enough to kill someone when I get confronted, and when I get pissed, I have more adrenaline than a crack-snorting elephant with a hormone problem.
To summarize: I'm normally a great, sane, calm collected person. I'm usually OK. But when it comes down to life or death, I'm not OK. Not at all.