The Cloud of Unknowing, ed. by Evelyn Underhill, , at sacred-texts.com
How a man should have him in beginning of this work against all thoughts and stirrings of sin.
AND from the time that thou feelest that thou hast done that in thee is, lawfully to amend thee at the doom of Holy Church, then shalt thou set thee sharply to work in this work. And then if it so be that thy foredone special deeds will always press in thy remembrance betwixt thee and thy God, or any new thought or stirring of any sin either, thou shalt stalwartly step above them with a fervent stirring of love, and tread them down under thy feet. And try to cover them with a thick cloud of forgetting, as they never had been done in this life of thee p. 173 nor of other man either. And if they oft rise, oft put them down: and shortly to say, as oft as they rise, as oft put them down. And if thee think that the travail be great, thou mayest seek arts and wiles and privy subtleties of ghostly devices to put them away: the which subtleties be better learned of God by the proof than of any man in this life. p. 174