Modern people may feel that “yin and yang” is far away from us, but in fact, yin and yang are everywhere in our lives, and it is especially important for the health of modern people to understand the theory of yin and yang and arrange daily life, especially diet, in a reasonable way. For example, day and night are both different and connected, transforming each other; water and water vapor, water is stationary, water vapor is moving upward, both can transform each other. The human body is actually a unity of yin and yang, and the body and its functions are unified to form a complete human being. Only when yin and yang are harmonized and transformed can we call it a healthy human body. When it is mild, it is only a change of function, which is often not taken seriously, such as feeling fatigue, “body weight”, insomnia, loss of appetite, abnormal urination and defecation, etc. At this time, it is only a change of function, and there is often no organic pathology in the hospital, which is called sub-healthy state in modern medicine. At this time, if the state of yin and yang is not adjusted, further development, accumulation of time, will be somewhere in the pathology, to the hospital examination found real lesions. Secondly, modern people tend to pay more attention to the tangible lesions and not to the first stage. If you feel uncomfortable, go to the hospital, there is no problem, as if everything is fine, turn around and continue to stay up late, drink, smoke, and all kinds of bad lifestyle, a few years later the problem finally came, and can never return to the old. The first stage is that our body is telling us that we need to adjust, adjust what, adjust the yin and yang, this is the idea of “treating the disease before it happens” in Chinese medicine. If a person is active, speaks with a high voice, likes to have a lot of people around, drinks cold water or even cold drinks, he or she has a yang body type, and when he or she gets sick, these manifestations are yin deficiency; if a person is quiet, has a low voice, likes to be alone, drinks hot water, he or she has a yin body type, and when he or she gets sick, these manifestations are yang deficiency. We can judge our own constitution by these simple, if there is physical discomfort, belong to what kind of yin and yang bias, there are more complex and precise ways to determine. Some people may ask which is more important, the yin or yang of the body? The yin of the human body is the material body, and without the function of yang, it can only be a corpse, which must be combined to be called the human body. If I had to say which is more important, since the Yin body is already developed (except for children), I would say that the function of Yang is more important. To protect the Yang of the human body is to protect the function of the body and to protect the function of the organs. The body is like water in a kettle that boils and turns into water vapor that can flush the lid off the kettle, and the yin water takes on the function of yang. A healthy body will feel energetic, walk with a gust of wind, and feel refreshed, which the people call “essence”, which is the yang energy of the body. When you feel heavy, it means that for some reason the yang energy is not enough and the body becomes heavy, just like water vapor turns into water and sinks downward. We often hear the word “light body and prolong life”, have you ever thought about the reasoning behind it, how to achieve a light body and prolong life, combined with the reasoning we just mentioned, you will understand, the protection of Yang Qi is the only way.