St. Silouan the Athonite on the Saints and Monastics (amateur translation)
The world is upheld through the prayers of the Saints. And the monk is called, that he might pray on behalf of the world, for this is his whole being. In this resides his service, and because of this he should not be burdened by worldly cares. The monk must live in continuous continence. If, however, he is occupied by worldly cares, then he is forced to eat more, and from this comes injury in general, for he who eats as is appropriate cannot pray in a befitting manner. Grace loves us to live in a body withered through asceticism.