When do you let sleeping dogs lie?

When do you personally think enough is enough and move on from a grudge? Like if someone has done you wrong how long does it take you to move on?? And do you feel guilty if the issue comes up and you find yourself talking about it later, as if you really haven’t let go of the grudge (or does that not happen to you?)?

I ask because of a situation in my life and the whole thing got me thinking, I wonder if how other people react would help me make sense of my own problem.