The Spoiler King
In my experience, most people that do wrong to you in some fashion aren't really worth the energy of forgiveness, because in all likelihood, they'd do it again in a heartbeat and without a second thought.
A few years ago, I was talking with a group of people that I called 'friends' about a number of topics, and after a few incidents where they felt the need to argue pointlessly with me about an opinion that I have/had about their claims (which will remain unsaid), they proceeded to conspire against me, compare me to a nazi, satan, and a few others, and ultimately got an entire group (then, larger than it was) to leave me behind with an empty forum. That was all over an opinion.
Needless to say, I have never forgiven, nor will I ever forgive, them. Forgiveness does nothing to help me move on, and the more I hold onto something, the fresher it is in my mind. I never forget such an act, and I see no reason to waste energy trying to forget, seeing as how that would reopen me to the possibility of it happening again.
To me a resentment is the internal dialogue in my head reliving something that I felt wronged me in someway. You could hold onto a resentment for 50 years and the other person/people would never have a clue, by the end the resentment only ended up effecting you. Letting go of the resentment by accepting my part and how it effected me gives me the power to relieve myself of that burden I carry. By letting go of a resentment it loses its power over my life.
At first I wrote letting go of a resentment and forgiveness were different. After reading what I wrote I deleted it because letting go of a resentment may mean forgiving yourself for holding onto something that could be negatively affecting your life. Even in as small a way as being afraid to login somewhere or say a specific thing to people for fear of being judged again. Forgiving the other people is not essential to letting go of a resentment in my life today that's more to do with compassion and understanding for how my actions may have effected them.