I recently posted about breathing but forgot to mention one aspect I find particularly interesting. Evidently, breathing through your left nostril activates the parasympathetic branch of the autonomic nervous system (i.e. relaxes) and breathing through the right nostril the sympathetic branch (i.e. alerts).
I would be interested in anybody's experience. I have tried using just the left nostril during the day and night (to get back to sleep) and it seems to work well. It can potentially work for any situation where anxiety occurs. With more confirmations, I may mention it to my daughter who's 9yo son has mild autism to help him get over stressful situations more easily.
Method: I simply block the right nostril, breath in, release right nostril, hold breath in for a couple of seconds and breath out through both nostrils.... repeat 3 times.