Bring calm into your nervous system via breathing

Here is a short video that deals with the relationship between the breath and the emotions.  In a study, scientists discovered that when emotions are elicited in trial participants, their breathing pattern changes.  But the interesting thing is that the opposite thing also happens:  When breathing patterns are altered, the corresponding emotion is elicited.  Let’s allow Emma Seppälä to explain it:
Breathe Better: How to Improve Your Mind, Attention, and Memory
In the video, she demonstrates the yogic breathing technique known variously as Nadi shodhana or anuloma-viloma.  Alternate nostril breathing works just fine, too.