Breathe in. Breathe out. Just make your exhale last a tiny bit longer than your inhale, to help yourself calm down.
That’s it. Continue until you feel a bit better.
Why does this work to help you relax? Inhalation engages the sympathetic nervous system. This is the function that gives you energy, engages in fight or flight. Exhaling engages the parasympathetic nervous system. This is the function that relaxes you, otherwise known as “rest and digest”.
That’s the theory. Or maybe it’s just the placebo effect. Either way, it helps.