Personally, my way of dealing with those feelings that most people label "resentment" is to refuse to drag past baggage around with me. We store events in our brain in "folders"--so, I just don't drag those old folders out and open them (in my mind).
It is a lot of just letting go of the past. The past is over and history will never change itself. Living in the present makes letting go of the past much more possible. Yes, I have memories of things that happened (I don't have long-term memory loss, yet)--but the same sting that a grudge or resentment would carry is not there, any longer like it might have happened as an event was occuring.
Several other factors go along with this--that makes leaving baggage behind possible.
One is dealing with feeling as they happen and resolving them in the present.
For example, if someone does me wrong---I must feel the hurt and anger and call it what it is. Sometimes it can be healed--so that there is no need to have the feeling any longer. If it can't--the relationship must be changed....either by detachment or sometimes it means moving away from the relationship--disengaging or ending it, altogether.
It does involving a conscious decision to not let the past taint my present or my future.
For sure, I have had to end lots of relationships that were toxic enough to continue to hurt or anger me.
For major traumas that caused grieving---one must grieve and allow the event to take it's place in the past --- where it belongs...just a yellowed page in the book of history.
Another big thing is not to give too much importance to "the small stuff". I think that a lot of the stuff that disrupts our inner sense of peace is simply not worth the energy and importance we give it. So often--it is not what happens so much as the importance that we have assigned to it. I often have to ask myself the question: "How important is this in the scheme of things".
These things are much harder to deal with when it comes to genetic family--for me, at least.
Much easier with other voluntary relationships.
Liz--I am sharing my general approach to this subject because you asked the questions.
This reflects my own life experience with this particular subject. I don't think that I ever use the word "forgiveness", very much. I have a different set of words for that.
dandylion