It may be a co-worker who feels slighted because of something you said at a meeting, a driver you inadvertently cut off on the way to work or a neighbor who's upset because your tree has branched too far into his yard.
It's almost impossible to go through life--or even a week--without someone becoming upset with you. It happens.
So how do you deal with it?
There's an easy technique recommended by de-escalation experts called the balloon technique. It works like this:
Imagine the other person's anger is like a balloon filled with air. If you get angry back, all you're doing is adding more air to the balloon.
Instead simply let the person vent until he has communicated his frustration completely. (If he asks questions, say you prefer to hear him out fully before answering.)
Letting the other person vent with little or no interruption will help to "deflate the balloon" thereby de-escalating the tension. Then you'll be in a better position to deal with the situation.