I don't view holding grudges as a practical solution to being significantly slighted. I've found it much easier to let go of whatever negativity I associate with the person that wronged me by removing them from my life in the same way that one would amputate a gangrenous limb; if that's a luxury I can't afford, I'll simply go passive and try to be willingly oblivious until somebody gives me a 100% justified reason to explode. However, justification alone usually isn't enough to put me on the offensive, since I pride myself on my willingness to make an effort to stay above interpersonal pettiness. It's usually more gratifying to let someone run out of steam and feel impotent than to meet them on their level and validate whatever they're doing, and you'll gain far more support from anybody else indirectly involved if you stay classy.
If you fuck up in a way that even I can't forgive, though, I won't rest until you're hurting at least as badly as I am. The fact that I actively repress my aggressive instincts when confronted can lead to some high-pressure buildup if the other party decides to escalate the situation to the breaking point, and since getting an extreme reaction from me requires a calculated amount of deliberation and effort, when it gets to that point it's pretty easy for me to flip the safety off and unload as much spite and anger into the other person as humanly possible, whether it be by going out of my way to destroy their self-esteem, or (less often) simply decking them.
