Needless to say, as a pastor I deal with that a lot. I know how hard it can be, and how vital to any healthy relationship.
I attended a mediation training earlier this year and have been reading about healthy communication quite a bit. It's fascinating how quickly things can go bad, and how it all comes down to the same issue: misunderstandings and things that were left unsaid.
It's hard to be honest when someone hurt you or you're upset about something they did.
It's easier to try to forget about it. At least it seems easier in the moment. In the long run, it will catch up with you. That pain or anger is not going away unless it's expressed. It will fester. And it will come out one way or another.
Instead, let your emotions come down to a legal level. Really think through what happened. Try to see both sides of the story. And then sit down with the other person and tell them how you feel. Don't attack them with a laundry list of things they did or didn't to. Just tell them how you feel. "I feel hurt. I feel betrayed. I feel disrespected. I feel angry." Speak your truth. Allow the other person to ask questions so they can truly understand you. You may even want to ask them to repeat what they heard you say to make sure they understood.
If the other person is willing to listen to you - give them time to calm down first, too, and make sure they are ready - then healing is possible. You'll be amazed.
I'm not saying this is easy. It's not. And depending on the individual situation it may not always accomplish what you had hoped. But expressing your feelings, speaking from your own experience and being honest with yourself and with the other person, will allow for you to process the whole situation, and help you to move on.
Give it a try. What have you got to lose?