The Classic of Medicine

“In the old days the sages treated disease by preventing illness before it began, just as a good government or emperor was able to take the necessary steps to avert war. Treating an illness after it has begun is like suppressing revolt after it has broken out. If someone digs a well only when thirsty, or forges weapons only after becoming engaged in battle, one cannot help but ask: Aren’t these actions too late?”

Taoism
The Yellow Emperor's Classic of Medicine

Ni, Maoshing, translator. The Yellow Emperor's Classic of Medicine: a New Translation of the Neijing Suwen with Commentary. Shambhala, 1995, [Chapter 2,The Art of Life Through the Seasons].