Healthy relationships are based on respect and have room for both. Attack the problem, not the other person. Healthy relationships don't blame. Don't assign feelings or motives. Let others speak for themselves.
Healthy relationships recognize each person's right to explain themselves.
Stay with the topic. Don't use a current concern as a reason to jump into everything that bothers you. Healthy relationships don't use ammunition from the past to fuel the present. It goes a long way in making things right again. Healthy relationships can admit mistakes.