Totally NOT a debate about the veracity of the gospels

[Angrboda]

My entire life I've been a push over, because that's what I thought god wanted from me. Turn the other cheek, never standing up for myself. I was bullied, but always thought reacting in love would be the best punishment for them. Turns out, not so. Now that I've come into my own and learned to stand up for myself and be assertive (within reason of course), I have a better self esteem and lots of truly great close friends. So that "turn the other cheek" isn't always for the best. Yes, there are moments when it's the best course of action, but I like being free to decide when that is.

From the Wikipedia:
"Tit for tat is an English saying meaning "equivalent retaliation". It is also a highly effective strategy in game theory for the iterated prisoner's dilemma."

The tit for tat strategy has been shown to be productive in certain constrained versions of competition. However, in other models of competition more closely resembling real life, it's not so clear that it is the most productive strategy. Indeed, psychologically, we tend to "over punish" defectors in real life instances of social behavior, even when doing so is objectively against our own self-interest. So it would seem that in real life, there are things going on that aren't adequately accounted for by this example from game theory.