4x4 breath techniques.  Interestingly it was recommended by my company in a monthly health and safety training session but I was already doing it because it's built in to my Garmin watch. It's a breath focusing technique that calms the mind and the body. 
-Breathe in through nose 4s
-Hold 4s
-Out through mouth 4s
-Hold 4s
Repeat 

Works like a charm! 

 Also a great exercise for improving lung capacity. Try increasing the breath lengths and reps. Can be done in the sauna for added effect.