St. Gregory the Theologian: Remembrance of God

It is more important that we should remember God than that we should breathe: indeed, if one may say so, we should do nothing else besides. I am one of those who approve of the precept that commands us to "meditate day and night" (Ps 1:2; Josh1:8), to tell of the Lord "evening, and morning, and at noon" (Ps 55:17), and to "bless the Lord at all times" (Ps 34:1), or in the words of Moses, "when we lie down, when we rise up, when we walk by the way" (Deut 6:7), or when we do anything else whatever, and by this mindfulness be molded to purity.
+St. Gregory the Theologian, from On God and Christ, The Five Theologian Orations and Two Letters to Cledonius, Oration 27, #4