Breathe deeply in and out through the left nostril with a light hold at the top and bottom of the breath. I like to do 7 seconds on the inhale, 3 second hold, 7 seconds on the exhale, 3 second hold.
You can always modify the time to make it more comfortable for yourself.
This is a great breath technique for times when you feel an urge to reach for something outside of yourself that you know ultimately won't be in your best interest. Try this for 3 minutes and see how it works!