"For every minute you remain angry, you give up sixty seconds of peace of mind."
Getting away from whatever is upsetting you will make it infinitely easier to calm down. Try to close your eyes and try to imagine yourself somewhere peaceful.
If your heart hammers with rage, slow it down by controlling your breathing. Count to three as you inhale, hold your breath in your lungs for three more seconds, and count to three again as you exhale.
If you're still having a difficult time calming down, imagine yourself in a scene you find incredibly relaxing. It could be your childhood backyard, a quiet forest, a solitary island - whatever locale makes you feel at home and peaceful,
Positive Self Talk
When you're ready, 'discuss' the situation with yourself in positive and relieving terms.
Talk To Someone
If you're still upset, sharing your concerns with a close friend or confident might help.
After you've calmed down and established that you're ready to get over the incident, try to see the lighter side. By casting the incident in a humorous light, it can help you maintain positivity and avoid getting angry over the same thing again.