Consequently, it is at the time they are going about their spiritual exercises with delight and satisfaction, when in their opinion the sun of divine favor is shining most brightly on them, that God darkens all this light and closes the door and the spring of sweet spiritual water they were tasting as often and as long as they desired. . . . God now leaves them in such darkness that they do not know which way to turn in their discursive imaginings. They cannot advance a step in meditation, as they used to, now that the interior sense faculties are engulfed in this night. He leaves them in such dryness that they not only fail to receive satisfaction and pleasure from their spiritual exercises and works, as they formerly did, but also find these exercises distasteful and bitter. … This change is a surprise to them because everything seems to be functioning in reverse. 

St John of the Cross ‘Dark Night of the Soul’