Your breath is directly connected to your nervous system. Fast, shallow breathing signals danger. Slow, deep breathing signals safety. You can consciously shift from stressed to calm in under a minute just by changing how you breathe.
This isn't woo-woo. The vagus nerve connects your breath to your heart rate, digestion, and stress response. Slow exhales activate parasympathetic ("rest and digest") mode. It's biology.
Used by Navy SEALs for stress management:
This takes about 1 minute and measurably reduces cortisol.
Dr. Andrew Weil's relaxation technique:
The long exhale activates the calming response. Good for anxiety or before sleep.
The fastest way to calm down (Stanford research):
This naturally happens when you cry or sigh. Doing it consciously triggers the same calming effect.
When you need to wake up, not calm down:
This is the opposite of calming breathing and genuinely increases alertness.