I was never the fighting type. To this day, I'm still not. In school I was picked on, sure, like everyone was. But it never got physical, until one day...
I had to take two buses to high school. I'd get on one, switch buses at a different high school, and take the second one to mine. One day, while waiting for the bus at the switch point, two BIG guys known for being jerks to everyone were horsing around nearby (6"6, 250+ both of them). One was getting the better of the two, and pushed his friend on the ground. They both started laughing. I thought it was funny, so I started laughing too. The one on the ground didn't like that. He got up and came over to me with the usual threats of violence. Yawn.
Then, he pushed me. So hard, I felt something pop in my spine, and it hurt. Bad.
That was it. I jumped into the air (he was WAY taller than me) and punched down as hard as I could. The blow landed on the bridge of his nose, and I felt it crack under my hand. He went down a second time, holding his nose. His buddy looked at me scowling, so I yelled "YOU WANT SOME?!" and he looked away. I had just beaten two bullies with one punch.
That fight was an epiphany for me. It showed me that I don't have to take the crap that people want to dish out, so I don't. Nowadays, you can't settle your arguments with just your fists anymore. Even if you win, they'll come back with buddies or a gun for revenge. So I carry, and I don't worry about it.