20. The man engaged in spiritual warfare should simultaneously possess humility, perfect attentiveness, the power of rebuttal, and prayer. He should possess humility because, as his fight is against the arrogant demons, he will then have the help of Christ in his heart, for ‘the Lord hates the arrogant’ (cf. Prov. 3:34. LXX). He should possess attentiveness in order always to keep his heart clear of all thoughts, even of those that appear to be good. He should possess the power of rebuttal so that, whenever he recognizes the devil, he may at once repulse him angrily; for it is written: ‘And I shall reply to those who vilify me; will not my soul be subject to God?’ (Pss. 119:42; 62:1. LXX). He should possess prayer so that as soon as he has rebutted the devil he may call to Christ with ‘cries that cannot be uttered’ (Rom. 8:26). Then he will see the devil broken and; routed by the venerable name of Jesus — will see him and his dissimulation scattered like dust or smoke before the wind.
29. Be watchful as you travel each day the narrow but joyous and exhilarating road of the mind, keeping your attention humbly in your heart, reproaching yourself, ready to rebut your enemies, thinking of your death and invoking Jesus Christ. You will then attain a vision of the Holy of Holies and be illumined by Christ with deep mysteries. For in Christ ‘the treasures of wisdom and knowledge’ are hidden, and in Him ‘the fullness of the Godhead dwells bodily’ (Col. 2:3, 9). In the presence of Christ you will feel the Holy Spirit, spring up within your soul. It is the Spirit who initiates man’s intellect, so that it can see with ‘unveiled face’ (2 Cor. 3:18). For ‘no one can say “Lord Jesus” except in the Holy Spirit’ (1 Cor. 12:3). In other words, it is the Spirit who mystically confirms Christ’s presence in us.
30. 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.
39. The devil, with all his powers, ‘walks about like a roaring lion, seeking whom he may devour’ (1 Pet. 5:8). So you must never relax your attentiveness of heart, your watchfulness, your power of rebuttal or your prayer to Jesus Christ our God. You will not find a greater help than Jesus in all your life, for He alone, as God, knows the deceitful ways of the demons, their subtlety and their guile.
40. Let your soul, then, trust in Christ, let it call on Him and never fear; for it fights, not alone, but with the aid of a mighty King, Jesus Christ, Creator of all that is, both bodiless and embodied, visible and invisible.
41. The more the rain falls on the earth, the softer it makes it; similarly, Christ’s holy name gladdens the earth of our heart the more we call upon it.
42. Those who lack experience should know that it is only through the unceasing watchfulness of our intellect and the constant invocation of Jesus Christ, our Creator and God, that we, coarse and cloddish in mind and body as we are, can overcome our bodiless and invisible enemies; for not only are they subtle, swift, malevolent and skilled in malice, but they have an experience in warfare gained over all the years since Adam. The inexperienced have as weapons the Jesus Prayer and the impulse to test and discern what is from God. The experienced have the best method and teacher of all: the activity, discernment and peace of God Himself.
Excerpt from the Philokalia – St. Hesychios the Priest “On Watchfulness and Holiness”