The full form — “Lord Jesus Christ, Son of God, have mercy on me, a sinner” — is often shortened in practice. The prayer is repeated continuously, first aloud, then under the breath, then silently in the mind, and finally — the hesychast tradition teaches — it “descends from the head into the heart” and becomes unceasing.
The Russian spiritual classic The Way of a Pilgrim presents the practice through a wanderer’s journey. The Philokalia is its deepest textual source.