When does resentment feature in a relationship?
I think resentment starts when a person feels they’ve sacrificed their own interests to the other person, and the other person doesn’t reciprocate. That’s why relationships should be equal without a sense of self-sacrifice on either person’s part. We shouldn’t be legalistic about things — measuring how much we give and get, but there ought to be a feeling that the give-and-take is more or less equal in the long run.