After entering winter, "getting up early and going to bed late, waiting for the sunshine" is the basic requirement of health preservation. This means that people must go to bed early and get up late in the cold winter. Going to bed early nourishes the human yang and keeps the body warm. It is best to get up after the sun comes out. At this time, the human body's yang is rising rapidly, and the content of adrenocortical hormone in the blood is gradually rising. Get up at this time, you will be clear-headed and quick-thinking. Moreover, the concentration of negative ions in the air is high in the morning, which is also very beneficial to the human body.