1 The hardest thing in life is to have control over one’s heart. To cultivate the Dao is to temper one’s heart. All saints of the three religions (Buddhism, Daoism, and Confucianism) took the “mind” as the main principle of cultivating the Dao.
2 Confucianism talks about “rectifying the mind and making the will sincere.” Buddhism advocates “seeing into one’s original nature.” Daoism stresses “tempering the mind.”
3 Human desires are insatiable. To temper the mind is to refine the mind that is full of desires until nothing is left. The goal is to empty the mind, to have no thoughts, no feelings and no self.
4 If one can temper the mind to be un- aroused, treat wealth and fame as passing clouds, and treat drinking, sex, and insatiable thirst for wealth and anger as dung, he will be able to incur not a single thought and all thoughts die out. It is to turn an ordinary person’s mindset to Dao mindset, which is the original heart.
5 A Chinese adage of sixteen characters says: “Human hearts are unpredictable and are prone to do evil; the development of everything always begins from something small, thus the ruler of a country needs to be keen in senses and judgment, and always takes preventive measures; he should persistently explore the truths of all matters with an undivided mind and does not allow anything to interfere with his judgment; he needs to follow the law of nature and takes unbiased approach in running the country.”  This explains the secret knowledge of what tempering the mind is all about.
Kazan Kai Kan (Kazan Conference Center), Tora no Mon, Tokyo, Japan, November 19, 1983
 The last four Chinese characters of the adage were the personal advice from Yao to his successor, Shun in running the country; when Shun passed his personal advice to Yu, he added the first twelve characters. Yao, Shun, and Yu were three outstanding tribal leaders after the legendary Yellow Emperor in ancient China.