There is a book called The Way of the Pilgrim. It is the story of a unnamed peasant who seeks out someone who will teach him how to fulfill the biblical command to “pray without ceasing.” He wanders through Russia and Siberia seeking out church authorities and religious people…He is about to come away empty handed when at last he meets someone who teaches him the Jesus Prayer.
“Lord Jesus Christ, Son of God, have mercy on me.”
He learns to repeat it as many as 12,000 times a day without effort.