What does the separation of yin and yang in traditional Chinese medicine mean?

Chinese medicine believes that the composition of the human body is yin and yang. The so-called coordination of yin and yang, all diseases are not born. The separation of Yin and Yang refers to the incompatibility and disharmony of Yin and Yang in the body, which easily leads to the excess of Yang in the body or the decline of Yang, leading to the disharmony of the body and many diseases.