In earlier days, people lived a more simple life. Today, people lead on-demand, hysterical, impulsive lives. Ignoring the subtle alterations of yin and yang which influence all, they become confused, exhausted, and frustrated. However, even today one can restore wholeness and clarity to one's mind.
Knowing that daybreak will come, that autumn follows summer, you can rest peacefully at night. When you understand the fluidity of yin and yang, you also begin to perceive the constancy behind them: the boundless, depthless Tao. To see this is the pinnacle of wisdom.