Some people act “nice” in order to get approval. Instead of sharing their real opinion, or showing their real feelings, they instantly agree and smile to avoid momentary rejection, pushback or the effort of working out a compromise. To be included, they withhold what they need to give the other person what they think they need. The problem is they aren’t being themselves, nor getting what they want. 

The nice person starts keeping a hidden score of all of the times they secretly didn’t get what they needed. Additionally, they resent other people being their true selves and getting their needs met. Now the nice person is seething with anger, and that rage leaks out in passive-aggressive words and actions. Instead of saying, no, they don’t want to do something, they agreed to it, but then ghost other people. People start avoiding the nice person because their words have a cut to them, their actions start hurting rather than helping or they can’t be trusted to follow through.

Finally, the nice person gets confronted for their passive aggressiveness or harmful actions. The nice person blows up, dumping out their weeks, months and years of rage and frustration. Horrified at seeing the failure of self-control through the eyes of another person, the nice person totally withdraws, thus ending the relationship altogether.