Wim Hof is really good, the calmness you feel after the breathing is unmatched.

There all these small techniques for managing emotions that are just not well known. If you need to calm down in the moment for example, doing a simple inhale for 4 seconds, hold for 2, exhale for 8 can make your stress melt away. Or in really stressful situations, try grabbing an icepack and holding it for a minute.