Visualize a peaceful scene. Close your eyes and imagine your favorite place in the world, whether it’s the beach where you used to vacation as a child or the beautiful lake you still remember from your teenage days. It can also be a scene from a place you’ve never been before; a forest, a field of flowers, or a beautiful landscape. Pick a place that makes you instantly feel more calm and at peace and you’ll quickly find your breath returning to normal. 

• You can even find your “go to” scene — the scene that calms you down any time you close your eyes.
• Focus on every little detail. The more details you see, the more you can pull away from your angry thoughts.

Source: wikiHow