It depends on what you consider self-defense.
http://en.wikipedia.org/wiki/Self-defense
The best way of defending yourself is de-esclation. After that, avoidance, but in the case of bodily harm, you have no choice but to counter it. Once you start defending yourself on the physical front, it's hard to stop. We don't live in the stone ages man. Fights aren't normal unless your in sports or hang out in the kind of environments that breed fights. To keep from killing someone, you would have to be trained. Kids aren't really taught how to defend themselves in school. This is Florida. This ain't China. We don't hold Tai Chi classes here. I'm surprised that kid
only got stabbed only 12 times.