[~Misguided Ghosts~]

Making peace can definitely be difficult sometimes. I think you've already completed the first step by saying you're not mad at them. I think it comes down to radically accepting what you can't change. That doesn't mean you have to be happy with how things turned out. It means that you accept that this is what has happened and you have done the best you could given the situation at hand. It may be worth trying to avoid contact with the people who won't let things go. Ignore them so they're not getting a reaction out of you.