Maybe resentments are really about grief. We grieve the loss of things we had or thought we had, or things we expected to get that we didn’t. Resentments are sparked by an unmet expectation. Grief is the result of a perceived loss - and in the case of resentment, it’s an expectation not met that creates the sense of loss. Think about a resentment you currently hold or one you once had; you should be able to connect it with some expectation and perceived loss.
Remember what’s behind every resentment/anger? Fear is always the culprit! Fear, that “evil and corroding threat, always seems to fall into one of two types: fear of losing something we have or fear of not getting something we want. There you have it- some sort of loss, real or imagined. Resentment by definition basically means to “re-feel” and that is what grief is about -- feeling and re-feeling emotions related to a loss of some kind.
Grief is not linear. Sometimes recovering alcoholics or addicts will be surprised and even ashamed when resentment resurfaces towards a person whom they had already addressed via past 4th step work or therapy. Old feelings of grief (a.k.a. anger/resentment) can resurface when triggered by a new perceived loss… perhaps same person, new circumstance… or a different person, same circumstance. For example: suppose you get engaged and you are happy with your fiancé, but you find old feelings of resentment surfacing towards an old love who dumped you when you thought you were going to get engaged. Then you may wonder why these feelings would arise even when you do not feel resentment toward your current relationship, but it is perfectly normal for a new situation to trigger an old resentment. It simply is a signal that you have the opportunity to work through some other aspect or piece of the grief process from that old loss, and by working through it you can learn from it and avoid having it negatively affect future relationships.
When we manage to get through the anger/resentment, usually sadness and disappointment lie just below it. Again, those feelings – part of grief - are due to the perceived loss. Like with every process of grief, the final goal is acceptance. When one reaches acceptance, feelings of joyfulness - essentially the opposite of resentment - are once again possible thus making the challenging process of working through grief worth the hard work.