Resentments eat us up internally. St. Augustine said "It is lie drinking poison ad expecting the other person to die." We are the only ones injured in this situation. Do not give the space to other people's energy in your thought process. In other words, refuse to let someone else live rent free in your mind. Resentments usually come from unmet expectations. It isn't relevant if you knew about the unmet expectation or not. Someone makes up something in their mind, a story, if you will, How do you deal with that? Clear communication, apologies, forgiveness, understanding all have a place in stopping resentments.