Slower breaths that gently move the belly, used to lower tension and alarm that often travel with pain.
When pain rises, breathing often goes high and fast. A slower belly breath can tell the body it is allowed to stand down a little. It will not argue the pain out of existence.
How to
Sit or lie down. One hand on the chest, one on the belly.
Breathe in through the nose so the belly hand rises more than the chest.
Let the exhale be a little longer than the inhale. Two minutes is enough to start.
Stop if you get dizzy. People with some lung or heart conditions should ask a clinician first.