For various motives, such as jealousy, revenge, the desire to right some injustice, we wish to see someone harmed or at least to be made to feel extremely uncomfortable. If we act impulsively, in a fit of anger, we may wind up in jail facing a charge of assault or even murder.
Few situations justify killing someone.
Fortunately most of us do not lose our tempers easily. It's a lot safer that way. Often, too, the situation doesn't look the same to us the next morning, after we've cooled off and had a chance to think calmly and rationally about it. First, remember that while generally it is a good thing to keep your temper you are under no moral obligation to swallow anything and everything that someone tries to shove at you. You don't have to turn the other cheek while someone keeps on slapping you.