Assume Positive Intentions
You can probably imagine situations with colleagues, parents, students, or administrators where there are challenges. Assuming the person you are dealing with has positive intentions really can turn a negative interaction into a productive one.
I'm not saying that this mindset will completely change something negative into positive. However, changing it from negative or contentious to productive or problem-solving is huge. I constantly remind myself of this advice when I'm confronted with a tough situation. (If you haven't read about finding marigolds and avoiding walnut trees, read it now!)
However, most of us can't avoid the walnut trees forever. I have noticed that if I go into a conversation assuming that a person is coming from a place of concern for me or students (instead of attacking or complaining) I have a much better conversation and the end result is more positive. You can read a little more about this here. This can not always be easy to do, and might not work in every situation, but the success rate is high and the rewards are worth it.