The Cloud of Unknowing, ed. by Evelyn Underhill, , at sacred-texts.com
That a man should not presume to work in this work before the time that he be lawfully cleansed in conscience of all his special deeds of sin.
BUT if thou asketh me when they should work in this work, then I answer thee and I say: that not ere they have cleansed their conscience of all their special deeds of sin done before, after the common ordinance of Holy Church.
For in this work, a soul drieth up in it all the root and the ground of sin that will always live in it after confession, be it never so busy. And, therefore, whoso will travail in this work, let him first cleanse his conscience; and afterward when he hath done that in him is lawfully, let him dispose him p. 168 boldly but meekly thereto. And let him think, that he hath full long been holden therefrom. For this is that work in the which a soul should travail all his lifetime, though he had never sinned deadly. And the whiles that a soul is dwelling in this deadly flesh, it shall evermore see and feel this cumbrous cloud of unknowing betwixt him and God. And not only that, but in pain of the original sin it shall evermore see and feel that some of all the creatures that ever God made, or some of their works, will evermore press in remembrance betwixt it and God. And this is the right wisdom of God, that man, when he had sovereignty and lordship of all other creatures, because that he wilfully made him underling to the stirring of his subjects, leaving the bidding of God and his Maker; that right so after, when he would fulfil the bidding of God, he saw and felt all the creatures that should be beneath him, proudly press above him, betwixt him and his God. p. 169