The body and the emotion are mutually causal. When our emotions are bad, the body will metabolize and become susceptible to diseases; when a person has a chronic disease, the long-term state is that the bad emotions will increase. So we can use this law in reverse.
When we are in a bad mood, we can start from the body to regulate it and make the body more positive, such as doing the exercise we like, going to the place we like, or eating the food we like.
This change in frequency will affect the improvement of our mood. When our body metabolism decreases, we can find things that can make our mood high. When people are happy, their mood will improve and their body metabolism will also improve.
People who are chronically depressed have long-term constipation, which is the same reason.