Watchfulness cleanses the conscience and makes it lucid. Thus cleansed, it immediately shines out like a light that has been uncovered, banishing much darkness. Once this darkness has been banished through constant and genuine watchfulness, the conscience then reveals things hidden from us. Through the intellect it teaches us how to fight the unseen war and the mental battle by means of watchfulness, how we must throw spears when engaged in single combat and strike with well-aimed lances of thought, and how the intellect must escape being hit and avoid the noxious darkness by hiding itself in Christ, the light for which it longs.
~St Philotheos of Sinai
Prayerful Life 