Like a good athlete in the service of truth, the blessed Abba Pachomius, just like blessed Antony, often fought a good fight against the unclean attacks of the demons. Indeed, for a time he asked the Lord with urgent prayers that he might carry on without sleep for a while and keep vigil day and night in battle against his demon enemies, until at last he overcame them and threw them down, according as it says in the psalm, “I shall not turn till they are beaten” (Psalms.18.37). The Lord heard his prayers because of his persistence. How stupid and ineffective the demons are, for any one of us with unquestioning faith and a wholehearted burning desire is able to do battle with them, trusting in the help of our Saviour Jesus Christ.
It was the brothers who told us about this blessed father Pachomius, who as we have said was head of many monasteries in the Tabennisi region. They told us that he frequently used to say to the brothers, “As the Lord God is my witness I have often heard these filthy demons discussing among themselves the various tricks which they play against the servants of God and especially against monks. Some would say, ‘I am having to fight against a terribly difficult person, for as often as I put evil thoughts into his head he gets up at once and prostrates himself in prayer, with many sighs begging for divine help. When he gets up after a short while all I can do is get out.’  Another would say, ‘When I put thoughts into the heart of the one I am looking after he consents to them, makes them his own, and puts them into practice. So I often get him to explode in anger, get involved in quarrels, neglect his prayer, go to sleep during psalmody, and he doesn’t resist me one scrap.’  Therefore, my beloved brothers, you must always keep watch over your feelings and your mind, calling upon the name of our Lord Jesus Christ, and in obedience to the commandments of God turn to prayer and psalms, as the Apostle says, ‘Be instant in prayer and watchful.’ (
Romans 12.1). Our filthy enemies the demons will not be able to prevail against us if we keep constant watch over our hearts in fear and trembling.”
So this blessed father Pachomius taught the brothers how to be always mindful of the words of God for the salvation of their souls, and the brothers departed each to his own cell, working with their hands and meditating on what they had learned from the sacred Scriptures. Idle words were out of the question among them, they discussed among themselves only what they had learned from the holy Scriptures, strengthening them in the fear of God and lighting up their souls. 

Paradise of the Fathers