By the age of forty the Yin force in the body has been reduced to one-half of its natural vigor, and an individual's youthful prowess has deteriorated. By the age of fifty the body has grown heavy. The ears no longer hear well. The eyes no longer see clearly. By the age of sixty the life-producing power of Yin has declined to a very low level.
Impotence sets in.
Those who seek wisdom beyond the natural limits will retain good hearing and clear vision. Their bodies will remain light and strong. Although they grow old in years, they will stay able-bodied and vigorous and be capable of governing to great advantage. For this reason the ancient sages did not rush into the affairs of the world. In their pleasures and joys they are dignified and tranquil.