I realized that a source of unhappiness is expecting other people to do or say something without communicating with them first. People are not good mind readers, so you have to be clear about what you want and expect.
I wrote more about it here: https://moviewise.substack.com/p/communication-insights-from...
But the real realization is that you should not expect anything from anyone. You should be able to feel happy and satisfied no matter what other people do or don't do.
In other words, don't allow other people to control your happiness by setting yourself up to be dependent on what they say or do. It shouldn't matter to your contentment. If you can just accept things as they are and enjoy what you can without lamenting what could be, what could have been, what other people have—then you can be stronger and happier: