The Cloud of Unknowing, ed. by Evelyn Underhill, [1922], at sacred-texts.com
That in this work a soul is cleansed both of his special sins and of the pain of them, and yet how there is no perfect rest in this life.
MORE devices tell I thee not at this time; for an thou have grace to feel the proof of these, I trow that thou shalt know better to learn me than I thee. For although it should be thus, truly yet me think that I am full far therefrom. And therefore I pray thee help me, and do thou for thee and for me.
Do on then, and travail fast awhile, I pray thee, and suffer meekly the pain if thou mayest not soon win to these arts. For truly it is thy purgatory, and then when thy pain is all p. 178 passed and thy devices be given of God, and graciously gotten in custom; then it is no doubt to me that thou art cleansed not only of sin, but also of the pain of sin. I mean, of the pain of thy special foredone sins, and not of the pain of the original sin. For that pain shall always last on thee to thy death day, be thou never so busy. Nevertheless, it shall but little provoke thee, in comparison of this pain of thy special sins; and yet shalt thou not be without great travail. For out of this original sin will all day spring new and fresh stirrings of sin: the which thee behoveth all day to smite down, and be busy to shear away with a sharp double‑edged dreadful sword of discretion. And hereby mayest thou see and learn, that there is no soothfast security, nor yet no true rest in this life.
Nevertheless, herefore shalt thou not go back, nor yet be overfeared of thy failing. For an it so be that thou mayest have grace to destroy the pain p. 179 of thine foredone special deeds, in the manner before said—or better if thou better mayest—sure be thou, that the pain of the original sin, or else the new stirrings of sin that be to come, shall but right little be able to provoke thee. p. 180