Peace of mind can heal three thousand diseases. Peace of mind can calm the heart. Where does the valley come from?

The Doctrine of the Mean. The Book of Rites is a monograph on moral philosophy. In the thirteenth chapter, it is said that "peace of mind can cure 3, diseases, and peace of mind can calm the heart", which means that if a person can keep his mind calm, he can cure many diseases, people get sick, and often his heart can't calm down because of too much desire.