The power of the Jesus Prayer lies in its expression of humility and need. "Have mercy" is the cry of the humbled heart for the salvation that only God can give. We cannot save ourselves but we know someone who can, and this knowing causes us to cry out with all our hearts "Lord Jesus Christ, Son of God, have mercy on me a sinner." The Desert Fathers and Mothers consistently taught the need for humility:
Theodora said that neither asceticism, nor vigils, nor any kind of suffering are able to save. Only true humility can do that. There was a hermit who was able to banish the demons. And he asked them: "What makes you go away? Is it fasting?" They replied: "We do not eat or drink." "Is it vigils?" They said: "We do not sleep." "Then what power sends you away?" They replied: "Nothing can overcome us except humility alone." Amma Theodora said: "Do you see how humility is victorious over the demons."