"Four methods". Wan Mizhai, a medical scientist in the Ming Dynasty, pointed out: "There are four ways to maintain health: one is lack of desire, the other is caution, the third is punctuality, and the fourth is illness." What does this mean? There are four ways to maintain health: first, control sexual desire; Second, be cautious; Third, adapt to the season; Fourth, eliminate hidden dangers of diseases. The so-called no desire is just to make people's character last; The so-called caution is to maintain and stabilize people's vitality; The so-called law is to reconcile yin and yang, and the so-called disease is to be cautious. Perseverance in personality will not harm the roots of bad people, and maintaining stability and vitality will make people's limbs intact, yin and yang harmonious and not violate evil spirits. If they use drugs carefully, they will not be poisoned by drugs.