Generally speaking, prayer is the sole obligatory and indispensable occupation and virtue for all rational beings, both sentient and thinking, human and angelic. For this reason we are enjoined to the unceasing practice of the prayer [2].
Prayer is not divided dogmatically into types and methods but, according to our Fathers, every type and method of prayer is beneficial, as long as it is not of diabolic delusion and influence. The goal of this all-virtuous work is to turn and keep the mind of man on God. For this purpose our Fathers devised easier methods and simplified the prayer, so that the mind might more easily and more firmly turn to and remain in God. With the rest of the virtues other parts of man's body come into play and senses intervene, whereas in blessed prayer the mind alone is fully active; thus much effort is needed to incite the mind and to bridle it, in order that the prayer may become fruitful and acceptable. Our most holy Fathers, who loved God in the fullest, had as their chief study uniting with God and remaining continuously in Him; thus they turned all of their efforts to prayer as the most efficient means to this end.
There are other forms of prayer which are known and common to almost all Christians which we will not speak about now; rather we will limit ourselves to that which is called "noetic prayer", which we are always being asked about. It is a subject that engages the multitude of the faithful since next to nothing is known regarding it, and it is often misconstrued and described rather fantastically. The precise way of putting it into practice as well as the results of this deifying virtue, which leads from purification to sanctification, we will leave for the Fathers to tell. We paupers will only mention those things which are sufficient to clarify the matter and to convince our brethren living in the world that they need to occupy themselves with the prayer.
The Fathers call it noetic because it is done with the mind, the "nous", but they also call it "sober watchfulness" [3] which means nearly the same thing. Our Fathers describe the mind as a free and inquiring being which does not tolerate confinement and is not persuaded by that which it can't conceive on its own. Primarily for this reason they selected just a few words in a single, simple prayer, "Lord Jesus Christ, Son of God, have mercy on me", so that the mind would not require a great effort in order to hold on to a long, protracted prayer. Secondly, they turned the mind within, to the center of our reason, where it resides motionless with the meaning of the divine invocation of the most sweet Name of our Lord Jesus, in order to experience as soon as possible the divine consolation. It is impossible, according to the Fathers, for our all-good Master, being thus called upon continuously, not to hear us, He Who desires so much the salvation of men.
Just as a natural virtue that is aspired to can only be achieved by the conducive means, so also this holy work requires some nearly indispensable rudiments: a degree of quiet; freedom from cares; avoidance of learning about and spreading the "news" of things going on, the "giving and taking" as the Fathers put it; self discipline in all things; and an overall silence which stems from these things. Moreover, I don't think this persistence and habit will be unattainable for devout people who take an interest in this holy activity. The good habit of a regular prayer time, morning and evening, always about the same time, would be a good beginning.
With surety we have emphasized perseverance as the most indispensable element in prayer. Rightly it is stressed by St. Paul, "Continue steadfastly in prayer."(Col. 4:2) In contrast to the rest of the virtues, prayer requires effort throughout our entire lifetime, and for this reason I repeat to those who are making the attempt not to feel encumbered, nor to consider the need for endurance as a failure in this sober-minded work.
In the beginning it is necessary to say the prayer in a whisper, or even louder when confronted by duress and inner resistance. When this good habit is achieved to the point that the prayer may be sustained and said with ease, then we can turn inwardly with complete outer silence. In the first part of the little book (Way of the Pilgrim) a good example is given of the initiation into the prayer. Sound persistence and effort, always with the same words of the prayer not being frequently altered, will give birth to a good habit. This will bring control of the mind, at which time the presence of Grace will be manifested.
Just as every virtue has a corresponding result, so also prayer has as a result the purification of the mind and enlightenment. It arrives at the highest and perfect good, union with God; that is to say, actual divinization (theosis). However, the Fathers also have this to say: that it lies with man to seek and strive to enter the way which leads to the city; and if by chance he doesn't arrive at the endpoint, not having kept pace for whatever reason, God will number him with those who finished. To make myself more clear, especially on the subject of prayer, I will explain how all of us Christians must strive in prayer, particularly in that which is called monological [4] or noetic prayer. If one arrives at such prayer he will find much profit.
By the presence of the Jesus Prayer man is not given over to temptation which he is expecting, because its presence is sober watchfulness and its essence is prayer; therefore "the one who watches and prays does not enter into temptation." (cf. Matt. 26:41) Further, he is not given over to darkness of mind so as to become irrational and err in his judgments and decisions. He does not fall into indolence and negligence, which are the basis of many evils. Moreover, he is not overcome by passions and indulgences where he is weak, and particularly when the causes of sin are near at hand. On the contrary his zeal and devotion increase. He becomes eager for good works. He becomes meek and forgiving. He grows from day to day in his faith and love for Christ and this inflames him towards all the virtues. We have many examples in our own day of people, and particularly of young people, who with the good habit of doing the prayer have been saved from frightful dangers, from falls into great evils, or from symptoms leading toward spiritual death.
Consequently, the prayer is a duty for each one of the faithful, of every age, nationality, and status; without regard to place, time or manner. With the prayer divine Grace becomes active and provides solutions to problems and trials which trouble the faithful, so that, according to the Scriptures, "Everyone that calls on the Lord shall be saved." (Acts 2:21)
There is no danger of delusion, as is bandied about by a few unknowledgeable people, as long as the prayer is said in a simple and humble manner. It is of the utmost importance that when the prayer is being said no image at all be portrayed in the mind; neither of our Lord Christ in any form whatever, nor of the Lady Theotokos, nor of any other person or depiction. By means of the image the mind is scattered. Likewise, by means of images the entrance for thoughts and delusions is created. The mind should remain in the meaning of the words, and with much humility the person should await divine mercy. The chance imaginations, lights, or movements, as well as noises and disturbances are unacceptable as diabolic machinations towards obstruction and deception. The manner in which Grace is manifested to initiates is by spiritual joy, by quiet and joy-producing tears, or by a peaceful and awe-inspiring fear due to the remembrance of sins, thus leading to an increase of mourning and lamentation.
Gradually Grace becomes the sense of the love of Christ, at which time the roving about of the mind ceases completely and the heart becomes so warmed in the love of Christ that it thinks it can bear no more. Still at other times one thinks and desires to remain forever exactly as one finds oneself, not seeking to see or hear anything else. All of these things, as well as various other forms of aid and comfort, are found in the initial stages by as many as try to say and maintain the prayer, in as much as it depends on them and is possible. Up to this stage, which is so simple, I think that every soul that is baptized and lives in an Orthodox manner should be able to put this into practice and to stand in this spiritual delight and joy, having at the same time the divine protection and help in all its actions and activities.
I repeat once again my exhortation to all who love God and their salvation not to put off trying this good labor and practice for the sake of the Grace and mercy which it holds out to as many as will strive a bit at this work. I say this to them for courage, that they don't hesitate or become fainthearted due to the bit of resistance or weariness which they will encounter. Contemporary elders that we have known had many disciples living in the world, men and women, married and single, who not only arrived at the beginning state but rose to higher levels through the Grace and compassion of our Christ. "It is a trifle in the eyes of the Lord to make a poor man rich." (Sir. 11:23) I think that in today's chaos of such turmoil, denial and unbelief there exists no simpler and easier spiritual practice that is feasible for almost all people, with such a multitude of benefit and opportunity for success, than this small prayer.
Whenever one is seated, moving about, or working, and if need be even in bed, and generally wherever and however one finds oneself, one can say this little prayer which contains within itself faith, confession, invocation and hope. With such little labor and insignificant effort the universal command to "pray without ceasing" (1 Thes. 5:17) is fulfilled to perfection. To whatever word of our Fathers one might turn, or even in their wonderful lives, he will encounter hardly any other virtue given so much praise or applied with such zeal and persistence, so that it alone constitutes the most powerful means of our success in Christ. It is not our intention to sing the praises of this queen of virtues, or to describe it, because whatever we might say would instead rather diminish it. Our aim is to exhort and encourage every believer in the working of the prayer. Afterwards, each person will learn from his own experience what we have said so poorly.
Press forward you who are doubtful, you who are despondent, you who are distressed, you who are in ignorance, you of little faith, and you who are suffering trials of various kinds; forward to consolation and to the solution to your problems. Our sweet Jesus Christ, our Life, has proclaimed to us that "without Me you can do nothing." (Jn. 15:5) Thus behold that, calling upon Him continuously, we are never alone; and consequently "we can and will do all things through Him." (cf Phil. 4:13) Behold the correct meaning and application of the significant saying of the Scripture, "Call upon Me in your day of trouble and I will deliver you, and you shall glorify Me." (Ps. 49(50):15) Let us call upon His all-holy Name not only "in the day of trouble" but continuously; so that our minds may be enlightened, that we might not enter into temptation. If anyone desires to step even higher where all-holy Grace will draw him, he will pass through this beginning point, and will be "spoken to" [5] regarding Him, when he arrives there.
As an epilogue to that which has been written we repeat our exhortation, or rather our encouragement, to all the faithful that it is possible and it is vital that they occupy themselves with the prayer, "Lord Jesus Christ, have mercy on me", the so-called "noetic prayer", with a sure faith that they will benefit greatly regardless of what level they may reach. The remembrance of death and a humble attitude, together with the other helpful things that we have mentioned, guarantee success through the grace of Christ, the invocation of Whom will be the aim of this virtuous occupation. Amen.
by Elder Joseph of Vatopaidi (Spiritual Child of Elder Joseph the Hesychast)
source :http://orthodoxinfo.com/search.aspx?q=Jesus+Prayer