An anonymously written Russian book based in the 1800's about a about a very sweet, humble, selfless guy who goes on a pilgrimage after loosing his wife and farm. He reads the Bible constantly and wants to know what it means in Thessalonians when it says "pray without ceasing". So he sets out to find a teacher who will teach him how to pray incessantly and why. After walking for weeks and weeks the man finally finds an old monk who tells him that the prayer God really wants to hear is The Jesus Prayer
(Lord Jesus Christ, have mercy on me). The monk tells him how to repeat the prayer without ceasing and after practicing the pilgrim masters it. He says the prayer silently to himself over and over, when he's talking to others, reading, and even sleeping. To stop saying it causes him great unhappiness and pain after a while because it's become a part of him. The point of the book is to awaken the world to the benefits of saying the prayer to yourself constantly. "Enlightenment is supposed to come with the prayer, not before it. The idea, really, is that sooner or later, completely on its own, the prayer moves from the lips and the head down to a center in the heart and becomes an automatic function in the person, right along with the heartbeat."
The little pilgrim reads the Philokalia constantly in The Way of a Pilgrim.