The elder said to the brother: My son, the gaze goes before the heart just as the herald goes before the king, for wherever a man looks long, there his heart will also fall. If the eye becomes accustomed to pure things, the heart is ashamed to carry filth; if the eye learns stillness, the heart no longer endures turmoil; and if the eye flees from vanity, the heart has nothing left to feed on. The eye is the gate; the heart is the house. If you guard the gate, the house remains whole; but if you leave the gate open, do not wonder that your house is laid waste. Then the elder paused for a moment and added: Know this, my son: it is not the heart that leads a man into sin, but the gaze that does not turn back in time.
Apophthegm
A brother said to the elder: Father, if the eye is the gate, how can I close it without becoming blind to the world?
The elder replied: Do not close the gate—set a guard.
The brother did not understand and remained troubled, saying within himself: Who can be the guard of the eye?
Pustia Inimii 