It is the task of unceasing watchfulness – and one of great benefit and help to the soul – to see the mental images of evil thoughts as soon as they are formed in the mind. The task of rebuttal is to counter and expose such thoughts when they attempt to infiltrate our mind in the form of an image of some material thing. What instantly extinguishes and destroys every demonic concept, thought, fantasy, illusion and idol is the invocation of the Lord. And in our mind we ourselves can observe how our great God, Jesus, triumphs over them all, and how He avenges us, poor, base and useless as we are.
St. Hesychios the Presbyter, on watchfulness and holiness, Philokalia
People who have received grace are as if impregnated and with child by the Holy Spirit; but they may abort the divine seed through sinning, or divorce themselves from God through intercourse with the enemy lurking within them. It is the turbulence of the passions that aborts grace, while the act of sinning deprives us of it altogether. A passion- and sin-loving soul, shorn of grace and divorced from God, is the haunt of passions – not to say of demons – in this world and the next.
St. Gregory of Sinai, Philokalia
The mystery of prayer is not consummated at a certain specific time or place. For if you restrict prayer to particular times or places, you will waste the rest of the time in vain pursuits. Prayer may be defined as the intellect’s unceasing intercourse with God. Its task is to engage the soul totally in things divine, its fulfillment – to adapt the words of St Paul (cf. 1 Cor. 6:17) – lies in so wedding the mind to God that it becomes one spirit with Him.
-St. Nikitas Stethatos, Philokalia
Those who love true knowledge should also be aware that the demons in their jealousy sometimes hide themselves and cease from open spiritual battle. Begrudging us the benefit, knowledge and progress towards God that we derive from the battle, they try to make us careless so that they can suddenly capture our intellect and again reduce our mind to inattention. Their unremitting purpose is to prevent the heart from being attentive, for they know how greatly such attentiveness enriches the soul. We on the contrary, through remembrance of our Lord Jesus Christ, should redouble our efforts to achieve spiritual contemplation; and then the intellect again finds itself engaged in battle. Let all we do be done with great humility and only, if I may put it like this, with the will of the Lord Himself. St. Hesychios the Presbyter, On Watchfulness and Holiness
Be attentive to yourself, so that nothing destructive can separate you from the love of God. Guard your heart, and do not grow listless and say: ‘How shall I guard it, since I am a sinner?’ For when a man abandons his sins and returns to God, his repentance regenerates him and renews him entirely.
St. Isaiah the Solitary -The Philokalia, Vol.1
By its nature, water is soft while a stone is hard. However, when it runs along a
watercourse and drips on a stone, it slowly but surely makes a hole in it. Likewise, the word of God is soft while our hearts are tough. However, if a person frequently listens to the Word of God, his heart softens and becomes capable to accept the fear of God. St. Abba Pimen
When you sin, blame your thought, not your action. For had your intellect not run ahead, your body would not have followed. St. Mark the Ascetic