Laozi said: In ancient times, those who practiced the Dao were the principles of reason, emotion and nature, the art of governing the mind, nurturing harmony, maintaining moderation, enjoying the Dao and forgetting lowliness, and being content and forgetting poverty. There is no desire in nature, and without desire, one cannot obtain; there is no joy in the heart, and without joy, one does not act. What is not beneficial to nature, one should not accumulate virtue; what is not convenient for birth, one should not be slick and harmonious. If one does not indulge in unrestrainedness but follows a system, one can become the norm of the world. One should eat according to one's stomach, dress appropriately, live comfortably, and act in accordance with one's emotions. There is nothing left in the world, and all things are entrusted without benefit. How could one lose one's life because of wealth, poverty, nobility and lowliness? Those who remain so can be said to be able to understand the Dao.