In old times, people started working when the sun rose and put their feet up when the sun set. Having to rest earlier guaranteed enough energy for next day's work. People had no telephone nor Internet. Boring as it was, people were healthy, because the lifestyle corresponded to the courses of nature. Modern people, however, sit up late or sleep in the morning, putting their health at risk over time.

Regarding work and rest schedule, in Yellow Emperor's Inner Canon, "People should go to bed early and get up late in winter, just like the rise and set of the sun. Avoid cold and keep warm. Don't expose your skin. Otherwise, your body will be hurt". That is to say, people should follow the course of the rise and set of the sun. If not, people will get sick. However, to look beautiful, women today would rather wear flimsy stockings in cold winter. As a saying goes, cold is from feet. Cold feet will cause many health risks as well as a deficient and cold constitution in your body.

Why do we need to get up and sleep earlier? TCM divides 24 hours per day into 12 time units. Human organs are believed to reach the climax of their functions at certain time units. The liver works hardest to clean blood between 1 to 3 am. If we don't fall into deep sleep, the metabolism of liver cells will be affected. From 5 am to 7 am, the large intestine works actively. People need to get up to absorb nutrition and eliminate waste so as to have a fresh day.

Apart from sleeping and get-ting up earlier, sleeping position and posture are also important. Sun Simiao, or the King of Medicine, proposed the most comfortable position with head facing south and feet facing north, while lying on side, because our spine has several curves and lying flat on one's back is not good for the body. Sun Simiao was not only the King of Medicine, but also a master of preserving health. In his book Invaluable Prescriptions for Ready Reference, he warned us not to sleep too long because long sleep impairs Qi, not to stand too long because that may hurt bones, and not to walk too long because that may injure muscles. The balanced concept of preserving health is derived from the ancient philosophy and source of TCM theory.