My personal favorite is breathwork, but there are people who get activated/trigged by breathwork so YMMV.

Ocean breathing: inhale through the nose for a count of 5, and exhale through the mouth for a count of 5, without any pause in between. Continue for 2-5 minutes.

Earth breathing: imagine inhaling all the way from the earth through your left foot and leg, the air going to the base of your spine as you hold it there for 3 seconds, then releasing the air through your right leg and foot back to the earth.

Heart breathing: imagine inhaling air from the sky and the earth into your heart, holding it there for 5 seconds, then exhaling out of the front and back of your heart, with the air going to all of your cells.