I'm not a violent person - the biggest fights I've ever had were probably when I was about 11 or 12, and they were nothing at that.
I have taken part in "aggressive" sports and found ways to control my own body so that I know what I'm doing, for example, with my fists, or legs. Some people never have the chance to do this.
Over the age of 12, maybe 13, I've never hit anyone. Ever. Simply because there has never been a situation in which I felt it would do any good - because I have normal morals and don't think violence is a solution to anything.
I know, though, that if it came down to it, and someone started trying to get at me with nowhere to escape to, then I would be able to fight back. Sometimes it helps to be strong enough to defend yourself, because nobody who is trying to hit you will ever stop if you say "violence isn't right" or whatever.