Principles of Yin and Yang
The interdependence of Yin and Yang.
In nature: Without day, there would be no night. Without winter, there would be no summer. In the human being: There are active people, because there are passive people. Everything exists only in relation to each other. Yin and Yang are opposites but are also mutually dependent on each other. Yin nourishes Yang. Yang produces Yin. If Yang is weak, Yin is not produced sufficiently. If Yin is weak, Yang can no longer be sufficiently nourished. Yin can't exist without Yang, and Yang can't exist without Yin. Therefore, Yang Deficiency can originate from Yin Deficiency and Yin Deficiency can originate from Yang Deficiency. The Qi (Yang) of the Lungs supports the Heart in the Blood production. Vice versa is the Qi of the Lungs nourished by the Blood (Yin) of the Heart.