Regard the person you're angry at as a mirror.
"The Buddhist teachings say that we would not see faults in others if we did not have faults in ourselves. If we feel critical or angry at someone, it could be that the person is showing us something about ourselves we do not like. To counteract this problem, we must learn to accept the existence of that quality in ourselves, with patience and kindness.
"I sometimes feel annoyed by noisy, chatty people. I have the concept that people should be quiet, calm, and subdued. That is how I try to be, but when I look honestly at my mind, I realize that it's very noisy and chatty, almost constantly making comments about everyone and everything. Chattiness, in fact, is a quality of my own mind, but I don't like it and try to keep it hidden. When I see it in others I feel judgmental: 'You shouldn't be that way!' By working on being more accepting and tolerant of my inner chattiness, I can learn to be more accepting of that quality in others.
"Try this: bring to mind a person you feel angry or annoyed at, and ask yourself what exactly it is that you dislike in him or her. Once you have identified that, check: 'Is this something that I have in myself? Have I ever behaved like that?' If you are able to find in yourself the same thing (or something similar) that you don't like in the other person, the solution is to learn acceptance and forgiveness toward yourself. When you can be more tolerant and compassionate toward yourself, with whatever faults you have, you will be better able to accept others as they are, and less likely to get angry at them."