I'm not a particularly violent person, but I seem to get in fights every couple years or so. It's usually while trying to prevent my friends from being hurt, but once or twice I was just drunk around the wrong people at the wrong time. I'm a very laid back, easy going guy. It takes a very large amount of provocation to get me angry. That's good, because I go into red-rage blackout mode when that happens. In my early 20s, I knocked out a couple guys that were trying to pick a fight with my friends, and didn't remember it later. All I knew was my hands hurt, and everyone was looking at me weird.
The real lesson is: avoid. Talk your way out of it. You never know if some sore loser/winner might have or knife or gun, and nobody is more impulsive than in the heat of the moment. You could get hit with a brick or windshield wiper or ten thousand other things that can turn you into a drooling vegetable. Plus, the police could show up. You go to jail, where if you miss bail you lose your job. It is a butterfly effect of bad shit. It's just not worth it.