Jesus himself lived this way: "While being reviled He did not revile in return, while suffering He uttered no threats but kept entrusting Himself to Him who judges righteously" (1Pet2:23).
So it seems a bit of a surprise when we read on in Romans 12:
"But if your enemy is hungry feed him and if he is thirsty give him a drink for in so doing you will heap burning coals on his head" (v20)
How do we reconcile "not paying back evil for evil" with "heaping burning coals on his head"?!
The answer is found in passages such as 1Pet3:16 where we see that the opponent really heaps the burning coals on his own head:
"....keep a good conscience so that in the thing in which you are slandered, those who revile your good behaviour in Christ will be put to shame"
Here the Christian is being "slandered" and "reviled" but doesn't repay evil for evil - instead he continues with "good behaviour", he continues to maintain a "good conscience". The outcome? The opponent is "put to shame". He is shown to be the wrong-doer. He tried to heap burning coals on the righteous man's head but really only succeeded in doing it to himself.
Its the same again in Titus 2:7-8:
"In all things show yourself to be an example of good deeds, with purity in doctrine, dignified, sound in speech which is beyond reproach so that the opponent will be put to shame, having nothing bad to say about us"
If we remain "beyond reproach" at all times, those who seek to ambush us only ambush themselves:
"They say....'Let us ambush the innocent without cause'.....but they lie in wait for their own blood, they ambush their own lives" (Prov1:11-18)
As the passage in Romans 12 concludes:
"Do not be overcome by evil but overcome evil with good" (v21)