How much time, energy and effort do you spend being angry or staying upset with someone? Especially someone you really love. If that person disappeared tomorrow, how would you feel? Would you still be angry or would you regret your last feelings towards them?
Staying upset over time requires you spend energy reliving the thought and moment over and over again. It’s as though you have a wound that you refuse to let heal, you continuously pick at the scab causing it to bleed just so that you can remember what happened.
You feel justified in your anger only because you want the other person to see the world from your perspective, but they almost never will. Their world view is based on a collection of their own experiences so in their mind they are behaving appropriately.
I’m not suggesting that you excuse their behavior, especially if it is malicious towards you. What I am saying is fueling your own negative emotion by continuously thinking or talking about it doesn’t benefit either one of you. Remember, anger is only one of many responses you can choose to have for an event.