12 This single motive then is no slight one: and even taken by itself it would have sufficed to deter me from this dignity: but, as it is, another must be added not less than the former. And what is this? A priest ought to be sober minded, and penetrating in discernment, and possessed of innumerable eyes in every direction, as one who lives not for himself alone but for so great a multitude. But that I am sluggish and slack, and scarcely able to bring about my own salvation, even you yourself would admit, who out of love to me art especially eager to conceal my faults.
Talk not to me in this connection of fasting, and watching, or sleeping on the ground, and other hard discipline of the body: for you know how defective I am in these matters: and even if they had been carefully practised by me they could not with my present sluggishness have been of any service to me with a view to this post of authority. Such things might be of great service to a man who was shut up in a cell, and caring only for his own concerns: but when a man is divided among so great a multitude, and enters separately into the private cares of those who are under his direction, what appreciable help can be given to their improvement unless he possesses a robust and exceedingly vigorous character?
Source: On the Priesthood (New Advent)