Sir, I do too feel that one should not be madly driven for vengence... But, I'm sorry, I personally think that one could be (and on extreme conditions, should be) vindictive, if he's affected badly by a person or a group of people.
I had faced this type of problem in my juvenile days of school. People tend to think your forgiving gesture your weakness, and thus they keep 'bullying' you... More than that, excessive "good'ol" thing might get yourself lowered by your ownself, that causes major mental pressure.
Nonetheless, it's also permitted in our religion, but not exceeding the limit, the victim had faced...
Last but not the least, My great grandpa used to say one quote of G.B Shaw regarding these sort of things, that I wanna share, "It's too bad to be too good..."