When things get crazy intense and your stress level shoots through the roof your heart feels like it's going to pound right out of your chest and you become short of breath, the lack of oxygen contributing to your freak out.
So if you learn to control your breathing in times of major stress and anxiety you can calm down faster and keep a cool head when everyone around you is falling apart, like soldiers do when they use tactical breathing to stay calm in combat.
Clinical psychologist Belisa Vranich demonstrates this breathing technique used by the military in this Tech Insider video- she's the author of Breathe: The Simple, Revolutionary 14-Day Program to Improve your Mental and Physical Health so she knows a thing or two about how breathing techniques can better your life.
-Via Mental Floss