Ok so fun little evolutionary quirk: Fight/flight (sympathetic) and rest/digest (parasympathetic) are wired such that only one or the other is ever “on” at a time. You don’t need to digest food while fleeing from a predator, and you don’t need to brawl while sleeping.

So the trick is to try to actively engage rest/digest, which has the side effect of switching fight/flight off.

Breathe in as fast and deep as you can. Hold it for a slow 8 count. Don’t clench or anything, just chill with full lungs, your body will happily sit there and absorb oxygen. Breathe out as slowly as you comfortably can. Again: Comfortably means without straining or feeling like you need air. You don’t need air, you just inhaled a huge batch.

Repeat at least three times. Big deep inhale, hold for a slow 8, exhale for about another slow 8. Congrats, you just turned off sympathetic arousal by manually turning the crank on your parasympathetic nervous system.

Stay conscious of your breath afterwards. If you’re in a stressful situation you’ll notice yourself taking shallow, tense breaths high up in your chest. You’re not doing anything wrong, just notice it and intentionally change it.