It is as necessary for a man to say the Jesus Prayer as it is for a ship in danger to send out steadily the S.O.S. signal: Lord Jesus Christ have mercy on me.
One time St. Nicodemos, on a feast day, was walking toward the Great Lavra (on Mt Athos). On his way he came across a kellion where he spent the night. At midnight he saw an elder and his accompanying monks entering the church. He secretly went in also, and there he saw the elder and his subordinate monks uttering the Jesus Prayer ('Lord Jesus Christ, Son of God, have mercy on me'), sometimes in a kneeling position, sometimes standing up. And at the time of the Holy Communion, he saw all their faces shining only a little less dimly than the sun.
Blessed are those who acquire the habit of this heavenly practice (unceasing prayer in the name of Jesus), for by it they overcome every temptation of the evil demons, as David overcame the proud Goliath. It extinguishes the unruly lusts of the flesh, as the three men extinguished the flames of the furnace. This practice of inner prayer tames passions as Daniel tamed the wild beasts. By it the dew of the Holy Spirit is brought down upon the heart, as Elijah brought down rain on Mount Carmel.
Having withdrawn from the palace to the solitary life, Abba Arsenius prayed and heard a voice saying to him, 'Arsenius, flee, be silent, pray always, for these are the source of sinlessness.'
Whenever we are filled with evil thoughts, we should throw the invocation of our Lord Jesus Christ in their midst. Then, as experience has taught us, we shall see them instantly dispersed like smoke in air. Once the intellect is left to itself again, we can renew our constant attentiveness and our invocation. Whenever we are distracted, we should act in this way.
Those who have truly decided to serve the Lord God should practice the remembrance of God and uninterrupted prayer to Jesus Christ, mentally saying: Lord Jesus Christ, Son of God, have mercy on me, a sinner.
As soon as you wake up in the morning, pray for a while, saying: 'Lord Jesus Christ, Son of God, have mercy upon me.' Then your first work should be to shut yourself in your own heart, as if taking up position in an arena. Having established yourself there, bring yourself to the consciousness and feeling that your enemy and the passionate urge against which you struggle at the moment are already there, on your left, ready for immediate attack; therefore rouse against them a firm resolve to conquer or die, but never to submit. Realize also that on your right there stands, invisibly present, your Commander, our Lord Jesus Christ, with His Holy Mother and a host of holy Angels, with Archangel Michael at their head, ready to come to your aid. So take heart and be of good cheer.
What should one do so that the mind might be constantly occupied with God? If we do not acquire the three following virtues: love for God and men, continence, and the Prayer of Jesus, then our mind cannot be completely occupied with God. For love makes anger meek, continence weakens fleshly desire, and prayer draws the mind away from thoughts and banishes every hatred and high-mindedness.
I shall indicate to you the most direct and simple method to acquire the habit of silence: ...reflect as often as you can on the pernicious results of indiscriminate babbling and on the salutary results of wise silence. When you come to taste the good fruit of silence, you will no longer need lessons about it.
Continually say the Prayer [of Jesus] intensely, with zeal, with longing; only thus does one become strong in soul. Avoid idle words by means of all sacrifice, for they weaken the soul and it does not have the strength to struggle.
At first it may appear very difficult to you, but be assured, as it were from Almighty God, that this very name of our Lord Jesus Christ, constantly invoked by you, will help you to overcome all difficulties, and in the course of time you will become used to this practice and will taste how sweet is the name of the Lord. Then you will learn by experience that this practice is not impossible and not difficult, but both possible and easy. This is why St. Paul, who knew better than we the great good which such prayer would bring, commanded us to pray without ceasing. He would not have imposed this obligation upon us if it were extremely difficult and impossible, for he knew beforehand that in such case, having no possibility of fulfilling it, we would inevitably prove to be disobedient and would transgress his commandment, thus incurring blame and condemnation. The Apostle could have had no such intention.
To be here in church is the source of all blessings. When they leave here, it seems that a husband is more respectful to his wife and a wife is more kind to her husband, since it is not the physical beauty of the body that makes a wife loving, but the virtue of the soul, not cosmetics and beauty aids, not gold and rich clothing, but chastity, meekness, and constant fear of God. This spiritual beauty nowhere develops to such an extent as in this wonderful and divine place (church), where the apostles and prophets wash away, reform, and cleanse old sin and bring forth the brightness of youth; where they extinguish every stain, every blemish, every defilement of our soul .... Let us try, husbands and wives, to rejoice in our inner beauty.
The incessant invocation of God's name is a medicine which mortifies not just the passions, but even their influence. Just as the physician puts medications or dressings on a wound that it might be healed, without the patient even knowing the manner of their operation, so also the name of God, when we invoke it, mortifies all passions, though we do not know how that happens.
Prayer is the mind's dialogue with God, in which words of petition are uttered with the intellect riveted wholly on God. For when the mind unceasingly repeats the name of the Lord and the intellect gives its full attention to the invocation of the divine name, the light of the knowledge of God overshadows the entire soul like a luminous cloud.
The practice of the prayer of Jesus holy David, or more accurately the Holy Spirit by the mouth of David, offers to all Christians without exception: 'The kings of the earth and all people, princes and all judges of the earth, young men and maidens - let elders with the young praise the name of the Lord, for His name alone is exalted (PS. 148:11-13).' A literal understanding of the states enumerated here would be perfectly permissible, but their essential meaning is spiritual.