Long exhales, a humming breath, then a cold cue. Three steps that tell your vagus nerve you are safe. Free, guided, about one minute.
Press start. Breathe with the circle.
Done. That was one full reset. Twice a day for a week and it starts working faster.
Background: Gerritsen & Band (2018), Breath of life: the respiratory vagal stimulation model, Frontiers in Human Neuroscience; Jungmann et al. (2018) on facial cooling and heart rate. Educational, not medical advice.
Take it with you. The free BreatheFirst app has this and more: SOS Calm, a breathing garden, levels, Apple Health heart rate and HRV, and a voice check-in. No account, no ads in the way, works offline.
More free tools: 60-second reset Box breathing Physiological sigh Urge surf Printable sheet