"Say not, I will do to him as he hath done to me: I will render to the man according to his work." (Proverbs 24:29)
Did you get it? This verse is the so-called "Golden Rule," in reverse. Whereas our Lord commanded in Matthew 7:12, "Therefore all things whatsoever ye would that men should do to you, do ye even so to them" (in other words, treat others as you yourself would want to be treated); the wise man tells us there are those among us whose philosophy is "I'll treat you the way you treat me." In other words, "give as good as you get." These kinds of people pride themselves in never being blind-sided or taken advantage of, never coming out on the short end of the stick.
The truly bad thing about this kind of perspective is that you end up allowing other people to decide your conduct for you, since you always respond in kind. This makes for a very predictable, unimaginative (not to mention, unbiblical) lifestyle. Once someone especially adept at the art of irritation finds out this weakness in our character, and can always be sure of getting a rise out of us, we become fair game.
But what if—just, what if—when goaded, mocked, or even wronged, we responded with a soft answer (Prov. 15:1), or turned the other cheek (Matt. 5:39), or didn't answer back (Titus 2:9)? Now, wouldn't that be original? Wouldn't that prove that nobody but God can dictate our responses? What a thing!
Our Christianity is seen best, not in the way we act, but in the way we re-act.