《管子·乘马》
等到商品消耗光，才知道不足，这是不懂得适量的原故；等到事业完成后，才发觉商品过剩，这是不懂得合度的原故。不懂得适量，不知道适度都不行。而要懂得它们，也是有规律的。
货尽而后知不足，是不知量也，事已，而后知货之有余，是不知节也，不知量，不知节不可，为之有道。
It is not until the commodities are exhausted that we know they are insufficient. This is because we do not understand the appropriate quantity; it is not until the事业is completed that we find that there is a surplus of commodities. This is because we do not understand the appropriate degree. It is not enough to understand the right amount, but also the right degree. And to understand them, there are also rules.