Actually, two things.
First, take a full breath in, followed by another smaller breath to fill your lungs a little bit more. Then, breath out slowly letting the exhale take about four seconds. Repeat a few times until you feel a change in context.
The other thing: notice how your vision is narrow and focused now. Stressful situations do that. Expand your vision by extending your arm in front of you drawing an oval which sides touch the periphery of your vision. Imagine yourself in the middle of this oval. Repeat a few times until you feel a change in perspective.
You can do both simultaneously.
Your brain changes your breath and your vision when it’s stressed. Breath is held and vision is narrowed. Amazingly, changing your breath and vision changes your brain’s state too1.
The next step is to decide what the next step is, but with a calm breath and wide vision. Re-focus without fear.
When you’re under stress, this is going to be the last thing you’ll remember. To increase the chances of doing it, practice it daily when you’re not stressed.
There’s research. Too lazy to link. Try it, it only takes a few minutes. ↩