When in fear, trembling and unworthiness we are yet permitted to receive the divine, undefiled Mysteries of Christ, our King and our God, we should then display even greater watchfulness, strictness and guard over our hearts, so that the divine fire, the body of our Lord Jesus Christ, may consume our sins and stains, great and small.
For when that fire enters into us, it at once drives the evil spirits from our heart and remits the sins we have previously committed, leaving the intellect free from the turbulence of wicked thoughts.
And if after this, standing at the entrance to our heart, we keep strict watch over the intellect, when we ace again permitted to receive those Mysteries the divine body will illumine our intellect still more and make it shine like a star.
Forgetfulness can extinguish our guard over our intellect as water extinguishes fire; but the continuous repetition of the Jesus Prayer combined with strict watchfulness uproots it from our heart.
The Jesus Prayer requires watchfulness as a lantern requires a candle.
We should strive to preserve the precious gifts which preserve us from all evil, whether on the plane of the senses or on that of the intellect.
These gifts are the guarding of the intellect with the invocation of Jesus Christ, continuous insight into the heart’s depths, stillness of mind unbroken even by thoughts which appear to be good, and the capacity to be empty of all thought.
In this way the demons will not steal in undetected; and if we suffer pain through remaining centered in the heart, consolation is at hand.
The heart which is constantly guarded, and is not allowed to receive the forms, images and fantasies of the dark and evil spirits, is conditioned by nature to give birth from within itself to thoughts filled with light.
For just as coal engenders a flame, or a flame lights a candle, so will God, who from our baptism dwells in our heart, kindle our mind to contemplation when He finds it free from the winds of evil and protected by the guarding of the intellect.
The name of Jesus should be repeated over and over in the heart as flashes of lightning are repeated over and over in the sky before rain.
Hesychios the Priest (?6th-9th century): On Watchfulness and Holiness chs 101-105, Text from G.E.H. Palmer, Philip Sherrard, and Kallistos Ware (trans. and eds.) The Philokalia: The Complete Text, vol. I (Faber & Faber, London & Boston: 1979), pp. 179-180.