Letting go?

Hi All-
I’ve realized recently that I have a hard time letting go of old flames, hurt feelings from friends and family, etc.. I can’t pinpoint exactly why I hold on, but I do and I want to change that.
I am trying to find some healthy ways to process these feelings and let them go. I know it’s hard, but I want and need to. Holding on to hurt feelings makes me sad and I know it doesn’t have to be that way. Anyone have any healthy suggestions? Thank you!!