Sayings of the Desert Fathers

A brother said to an old man, “I do not know of any warfare in my heart.” The old man said to him, “Then you are a building open on all four sides. Whatever wishes to, goes in and out, and you do not notice. If you had windows and a door, and shut them so as to bar certain thoughts, you would soon realize how many there are outside, waiting to slip in and attack you.”