This book focuses on the way of keeping in good health from three aspects: eating, drinking and sleeping. Diet is the basic condition for human life. It is not enough for people to live healthy, happy, full of vitality and wisdom. We should also consider the rational distribution of diet to ensure that the intake of various nutrients needed by the human body is balanced and sufficient and can be fully absorbed and utilized by the human body. The application of daily food, according to different economic conditions and different physiological and pathological needs, can not only satisfy hunger, but also supplement nutrition to the body and be beneficial to health. The secret of longevity lies in adjusting diet. A reasonable diet can make people strong and live longer. And improper diet can lead to disease and premature aging. A reasonable diet is necessary. Avoid partial eclipse and monotonous diet. Otherwise, it will have a series of bad consequences.