Only children and fair fighting

Many times in the past when I have gotten into an argument, I have had a tendency to jump the gun and go straight to some of the meanest, most cruel responses that I can come up with. I have done this not only with friends, but with my parents as well. These days, I've been paying a lot of attention to how I respond to someone else's anger as well as my own frustration, and find myself holding back a great deal. Does anyone else here feel the same? Is this weight of irrational responses maybe caused by the lack of sibling rivalry growing up? Maybe an absence of a sense of fighting within boundaries?