On having any evil thought, one must call upon God's help, for, as St. Isaac of Syria said, we do not always possess within ourselves the strength to oppose evil thoughts, and there is no help in this matter but from God. Therefore, guided by the instructions of Nilus of Sinai, we need to assiduously pray, with sighing and tears, to the Lord Jesus Christ thus: "Have mercy on me, O Lord, and do not allow me to perish! Rout, O Lord, the demon attacking me. O my sure hope, make Thy sign over my head in the day of my battle with the demon! Overcome the enemy who is doing battle with me. O Lord, O Word of God, with Thy peace and quiet tame the thoughts that are assailing me!" Or, according to the instruction of blessed Theodore the Studite, on having unclean thoughts, pray using the Prophet David's words, 'Judge them, O Lord, that do me injustice and war against them that war against me' and then recite the entire 34th Psalm [Ps 35 in the KJV]; and as the hymongrapher wrote, "Gather together and collect my scattered mind, O Lord, and cleanse my wild heart. As Thou did unto Peter, grant me repentance, as unto the publican, sighing, as unto the loose woman, tears, that I might cry unto Thee: help me and rid me of foul thoughts! For, like ocean waves, my transgressions rise up against me, and like a ship in the deep, I am loaded down with my thoughts and intentions; but do Thou guide me into a quiet safe harbor. O Lord, save me as well through [my] repentance, for I mourn greatly over the weakness of my mind, for not of mine own will do I undergo truly involuntary changes - vacillation, assaults, defeats. Because of this I cry unto Thee: O Holy Trinity without Beginning, help me, and confirm me to stand firm in good thoughts and intentions, senses and feelings!"