אות-לט

When a person enters great holiness — such as when he draws close to the true Tzadik and the like — sometimes precisely then an impure nocturnal occurrence befalls him, G-d forbid. He should not fall in spirit on account of this — for on the contrary, sometimes this is a sign that he has drawn close to holiness, and sometimes it is a great good. (ibid., Ois 117)