St. Diadochus of Photiki: On Baptism and the Remembrance of God

 Before holy baptism grace encourages the soul towards good from the outside, while Satan lurks in its depths, trying to block all the intellect's ways of approach to the divine. But from the moment that we are reborn through Baptism, the demon is outside, grace is within...

It is a mark of one who truly loves holiness that he continually burns up what is worldly in his heart through practicing the remembrance of God, so that little by little evil is consumed in the fire of this remembrance and his soul completely recovers its natural brilliance with still greater glory.

+St. Diadochus of Photiki, from One Hundred Texts on Spiritual Knowledge and Discernment, The Philokalia, Volume 1

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