Why should Grain Rain's solar term "nourish the heart and strengthen the spleen"?

After the solar term in Grain Rain, the rainfall increased and the humidity in the air gradually increased. At this time, we can't break away from the track of natural environment changes in health care, and make the internal environment (physiological changes in the body) adapt to the changes in the external environment (external natural environment) through internal adjustment of the human body, thus maintaining normal physiological functions. "Su Wen's Life-saving Holography" says: "Man is born with the spirit of heaven and earth, and is formed by the method of four seasons." This means that the changes in nature between heaven and earth will inevitably directly or indirectly affect the internal environment of the human body, and maintaining the balance and coordination between the internal and external environment is the basis for avoiding and reducing the occurrence of diseases. Therefore, it is necessary to consider the solar terms in Grain Rain when keeping in good health, and adjust it selectively according to its climatic characteristics.