Studied judo for a bit, the sensei got annoyed that he couldn't make me tap out, even on the point where he was breaking my arm. eventually got kicked out for breaking a guys nose, though in my defence he was trying to strangle me, which has happened 6 times from 3 different people.
I have the killer instinct that makes me see red and lose control. i know it will most likely land me in serious trouble one day.
It's the reason i haven't been in a proper fight for a long time.
edit: i'm also an unbelievably fast obstacle course runner, so if it comes to it i'll get away, though i've never been one to back down.