I have a love-hate relationship with grudges.
I seem to love holding onto bitter resentment. I hate that I do. I guess it stems from never really ever having any closure from disputes that sort of pop up from seemingly nothing, and never really knowing why the thing that pissed me off happened.
Sometimes you'll never find out why bad things happen. Sometimes you'll never figure out why someone you loved or someone you thought was a friend takes you down a peg or three. But that's no reason to stop living and stop doing what makes you happy. I need to learn to accept that.
However... It does help a lot when someone apologizes.