A certain brother by the name of John came from the coastal country to the holy and great father Philemon (Abba Philemon: an Egyptian hermit during the 6th—7th century) and clasping his feet, said to him: ‘What must I do, Father, to be saved? I see that my mind is distracted, and wanders hither and thither where it should not.’ After a short silence, Philemon said to him:
‘This is a sickness suffered by those who are external, and it remains in you because your love of God is not yet perfect; up till now the warmth of the love and the knowledge of God has not yet arisen in you.’
The brother asked him, ‘What then shall I do ? ‘ ‘Go,’ answered the father, ‘and for the time being practice secret meditation in your heart; this will cleanse your mind of its sickness.’
The brother, not understanding what was told him, said to Philemon: ‘What is this secret meditation, Father? ‘ ‘Go,’ he answered, ‘preserve sobriety in your heart, and in your mind repeat soberly, with fear and trembling, ‘ ‘Lord Jesus Christ, have mercy upon me.” This is what the blessed Diadochos prescribed for beginners.’
The brother left him, and by God’s help and the prayers of the father he began to keep silence and to taste the sweetness of this secret meditation. But this lasted only for a short time. Since it suddenly departed from him and he could no longer maintain it or pray soberly, he came again to the father and told him what had happened. The father said: ‘Now you have trod a little way on the path of silence and inner practice and tasted of its sweetness. Therefore, keep it always in your heart. Whether you eat or drink, or talk to someone outside your cell or on the way somewhere, do not forget to recite this prayer with a sober and attentive mind, and to sing and meditate upon prayers and psalms.
Even if you are satisfying some essential need, do not allow your mind to be idle, but let it meditate and pray in secret. All the time— when you drop off to sleep or wake up, when you eat or drink, or talk with someone—keep your heart at work secretly, sometimes meditating on a verse from the Psalms, and sometimes praying, “Lord Jesus Christ, Son of God, have mercy upon me.” ‘
From the Life of Abba Philemon, The Art of Prayer, pp. 76,77