The ceaseless repetition of the name of Jesus is a form of prayer very dear to Greek and Russian Orthodox Christians, who find in this form of prayer the firm foundation of their prayer life and their spiritual life in general. I recommend that you read the book The Way of a Pilgrim to get some idea of the value of this prayer and the way it is practiced.
This is a form of prayer that has been highly developed among Hindus in India over a period of thousands of years. It is called the Remembrance of the Name. Mahatma Gandhi, who was a zealous advocate of this form of prayer, claimed that it brought with it the most extraordinary benefits for spirit and mind and body. He claimed to have overcome all his fears, even as a child, simply by ceaseless repetition of God's name. He said there was more power in its recitation than in the atomic bomb. He even went to the extent of claiming that he would not die of any sickness: that if he were to die of some sickness, people would consider him a hypocrite! According to him, reciting God's name with faith would cure a man of any disease whatsoever. Only he must recite the Name with all his heart and soul and mind during the time of prayer.
Outside the time of prayer, even a mechanical recitation of the Name will do. Through this seemingly mechanical recitation the Name gets into one's bloodstream, as it were, into the very depths of one's unconscious and of one's being — and, very subtly but surely, one's heart and life are transformed.
In this and in some of the following exercises, I propose some ways of reciting the Name in time of prayer. I limit myself mostly to the Name of Jesus. All the masters assert that any name of God will do to attain the benefits that this prayer brings with it. Some of you may want to take for your mantra the name of God that the Spirit cries out within our heart, Abba, Father.
Begin your prayer by asking for the help of the Holy Spirit. It is only in the power of the Spirit that we can worthily pronounce the name of Jesus . . .Then imagine Jesus before you. In what form do you like best to imagine him? As an infant, as the crucified Christ, as the risen Lord . . . ?
Where do you imagine him to be? Standing before you? Some are greatly helped to imagine the Lord as being enshrined within their heart . . . or within their head. Some of the Hindu masters recommend the center of the forehead, somewhere between the eyes . . . Choose the place that you find most devotional in which to imagine you see him . . .
Now pronounce the name of Jesus each time you breathe in or each time you breathe out . . . Or you may pronounce the first syllable of his name as you breathe in and the second syllable as you breathe out. If you find this too frequent, then pronounce the name after every three or four breaths. It is important that you do this gently, relaxedly, peacefully . . .
If you are in the same presence of others you will have to recite the name mentally. If you are alone, you may pronounce it vocally, in a soft voice.
If, after a while, you tire of pronouncing the Name, rest for a while, then take up the recitation again, somewhat as a bird does when it flaps its wings for a while and then glides for a while, then flaps its wings again . . .
Notice what you feel when you pronounce his name . . .
After a while, pronounce his name with different sentiments and attitudes. First pronounce it with desire. Without saying the words, Lord, I desire you, convey this sentiment to him through the way you recite his name.
Do this for some time, then take another attitude. One of trust. Through your recitation of his name say to him, Lord, I trust you. Go on, after some time, to other sentiments, to adoration and love and repentance and praise and gratitude and surrender . . .
Now imagine you hear him pronounce your name . . . as he pronounced Mary Magdalene's name on the morning of the Resurrection . . . No one will ever pronounce your name in quite the way Jesus does . . . With what sentiments does he pronounce your name? What do you feel when you hear him pronounce your name?
Among the Orthodox it is customary to recite the name of Jesus within the Jesus Prayer formula. The formula is "Lord Jesus Christ, have mercy on me." Here is a method for using this formula:
After a time spent in quieting yourself become aware of the presence of the risen Lord . . . Imagine him standing before you . . .Now concentrate on your breathing for a while, becoming aware of thei air as it comes into you and goes out . . .
When you breathe in say the first part of the formula "Lord Jesus Christ," and, as you do so, imagine you are breathing into yourself the love and grace and presence of the Lord Jesus . . . Imagine you are breathing into yourself all the loveliness of his being.
Then hold your breath for a brief moment in your lungs, and as you do this, imagine you are holding in yourself what you have breathed in, that your whole being is suffused with his presence and his grace . . .
As you breathe out say the second part of the formula, Have mercy on me . . . As you do this imagine you are breathing out of yourself all the impurities, all the obstacles you are putting to his grace . . .
The words "Have mercy on me" do not mean just "Pardon me my sins." Mercy, as the Orthodox used the word, means much more: It means grace and loving kindness. So when you are asking for mercy, you are asking for Christ's graciousness and loving kindness and for the anointing of his Spirit.
— Anthony de Mello in Sadhana, A Way to God: Christian Exercises in Eastern Form