The unity of form and spirit is the key to enjoying the years. God lives in form, and form is unified with God. Spiritual injury leads to physical injury, and spiritual death leads to physical death. This is the so-called "if God is absent, he will die, and if God is present, he will live". Mental decline is bound to be manifested in the form, such as dull eyes, dull complexion, weakness of limbs, poor food intake, thin body and so on. Because human spirit is dominated by the heart, ambition, will, soul and spirit are all dominated by the heart, so there is a saying that "the heart is the master of form". Therefore, conditioning the heart has become the key to regulating the body. Therefore, the theory of TCM health preservation emphasizes quietness and spiritual cultivation, because "quietness can strengthen the body, and you can live to 100 years old without illness" ("Eight Notes on Respect for Life"). Essence, qi and spirit are called the "three treasures" of the human body, and they are inseparable. Their ups and downs directly reflect the growth, development and even aging of human beings. Essence is the source of life, the basic substance that constitutes the human body and the material basis of various functional activities of the human body. Qi is the motive force of life activities, which is transformed from essence, and essence is the basis of qi. God refers to the manifestation of God's will and life activities in spiritual consciousness. Where there is essence, there is God. God is the concrete expression of the five internal organs, the essence of heaven and the highest dominant activity of the human body. It is a high generalization of spiritual consciousness, thinking activities and external manifestations of viscera essence, qi, blood and body fluid activities. Qin Shou's new book on providing for the aged once summed up the relationship between essence, qi and spirit: "The subject is God, qi is essence, essence is qi, and qi is food." Therefore, the abundance of God needs a material basis such as essence, and the fullness or deficiency of essence can directly affect the role of God. In view of this, a good health-preserving person must maintain the essence and achieve the harmony between essence and spirit.