"A person is called a ‘small city’ (Koheles 9:14, Nedarim 32b) and every organ in the body dwells in this city. When one wishes to place a tax, there are wealthy ‘citizens,’ such as thought, speech, the faculty of hearing, and the like. Then there are poor ‘citizens,’ such as the rest of the body, which one would tax by imposing fasts and afflictions. The result of this is that the entire body becomes weakened. Thus, you would be better off leaving the poor organs and demanding a great deal from the wealthy ones: the eyes, ears, mouth, and so on. The results will be far greater."
by Reb Zalman Aharon Shneersohn, known as the Razo, the oldest son of the Rebbe Maharash