Getting even doesn’t work.  The person who receives a blow always thinks it is harder than the one he gave out.  There are only two ways that a cycle of revenge ends.  One is death; the other is for someone to show enough strength to absorb the last blow without responding in kind.  Fighting tends to escalate: the longer a fight lasts, the more pain is inflicted on both sides.  The best time to stop a fight is to refuse to strike back after the first blow.