When referring to mental health, people are usually specifically addressing emotion regulation. The standard recommendation for emotion regulation is always consistency. Consistent sleep, consistent cardiovascular exercise, consistent nutrition. Humans are pretty resilient and can adapt to most things as long as they're consistent.
Otherwise instead of trying to calm down, the most practical approach is usually to slow down. Slow your pace where you can. You body calms, followed by your mind. Many people use breathing for this but the same can be done by doing your routines intentionally slower. Eating, brushing your teeth, picking up your phone after you hear a notification, just do it slow.