You ask a good question? Let's talk about the human defense system, the human defense system is yang qi, the efficacy of yang qi is a main defense, so that the positive qi storage, evil can not be dry, meaning that the person yang qi is strong, disease and evil qi will rarely be able to affect the human body. The second is the main warmth, the third is fixed, the fourth is the main gasification and so on.

When a person sleeps, yang qi into the yin, people can fall asleep, yang qi out of the yin, that is, sleep and wake up, Huangdi Neijing said, yang qi into the yin is sleep, yang qi out of the yin is awake. Is the meaning of the above, people wake up yang qi outside, the defense is strong, asleep, yang qi into the yin, the person's defenses down, false evil thieves wind, to avoid sometimes, when the person's defenses are down, the wind for the thieves evil just to take advantage of your body when the body of false and invasion of the human body. Often the wind will be mixed with other evils such as cold evil, dampness and so on common invasion of the human body. So when you wake up feeling, tiredness, fatigue, body aches and pains and other symptoms, when the activities will feel much better.

The best way is to sweat, so that the evil qi is discharged out of the body with the sweat, but some people are always in the cold house in summer without sweating, so that the qi shall not be diarrhea, because the evil qi, which is suffered at this time, is not discharged out of the body, but is latent in the body, which is the ambush of evil, and the onset of disease occurs when one's righteousness is more declined.