I found this quote profound:
He does not become a shaman simply by willing it, for it is not the shaman who summons up the spirits but they, the supernatural beings, who choose him.
The spirits may cause the chosen one to fall into hysterics, to faint repeatedly, to have visions, or to have similar symptoms, with these events sometimes persisting for weeks.
Eventually, in a vision or a dream, the being or beings who have chosen the shaman appear and announce their intentions. This call is necessary for the shaman to acquire his powers. The spirits first lavish the unwilling shaman-to-be with all sorts of promises and, if they do not win his consent, go on to torment him.
Known as “shaman illness,” these torments will anguish him for months, and in some cases for years—that is, for as long as the human does not accept the profession of shaman.