Then the old man crossed himself and spoke. “Thank God, my dear brother, for having revealed to you this unappeasable desire for unceasing interior prayer. Recognize in it the call of God, and calm yourself. Rest assured that what has hitherto been accomplished in you in the testing of the harmony of your own will with the voice of God. It has been granted to you to understand that the heavenly light of unceasing interior prayer is attained neither by the wisdom of this world, nor by the mere outward desire for knowledge, but that on the contrary it is found in poverty of spirit and in active experience in simplicity of heart”…Reject all other thoughts (you can do this if you will)…and repeat only the following words constantly, “Lord Jesus Christ, have mercy on me.” Compel yourself to do it always. If you succeed for a time, then without a doubt your heart also will open to prayer. We know it from experience…”
R.M. French trans. The Way of the Pilgrim and the Pilgrim continues His Way (San Francisco: Harper Collins, 1973) 7, 12-13.