The Cloud of Unknowing, ed. by Evelyn Underhill, , at sacred-texts.com
That in all other works beneath this, men should keep discretion; but in this none.
AND furthermore, if thou ask me what discretion thou shalt have in this work, then I answer thee and say, right none! For in all thine other doings thou shalt have discretion, as in eating and in drinking, and in sleeping and in keeping of thy body from outrageous cold or heat, and in long praying or reading, or in communing in speech with thine even-christian. In all these shalt thou keep discretion, that they be neither too much nor too little. But in this work shalt thou hold no measure: for I would that thou shouldest never cease of this work the whiles thou livest. p. 203
I say not that thou shalt continue ever therein alike fresh, for that may not be. For sometime sickness and other unordained dispositions in body and in soul, with many other needfulness to nature, will let thee full much, and ofttimes draw thee down from the height of this working. But I say that thou shouldest evermore have it either in earnest or in game; that is to say, either in work or in will. And therefore for God’s love be wary with sickness as much as thou mayest goodly, so that thou be not the cause of thy feebleness, as far as thou mayest. For I tell thee truly, that this work asketh a full great restfulness, and a full whole and clean disposition, as well in body as in soul.
And therefore for God’s love govern thee discreetly in body and in soul, and get thee thine health as much as thou mayest. And if sickness come against thy power, have patience and abide meekly God’s mercy: and all is then good enough. For I tell thee p. 204 truly, that ofttimes patience in sickness and in other diverse tribulations pleaseth God much more than any liking devotion that thou mayest have in thy health. p. 205