The next task now confronting him is to grow, as it were, into this higher self, that is, really to regard it as his own true self and to act accordingly. He realizes ever more clearly and intensely that his physical body and what he hitherto called his “I” are merely the instruments of his higher self. He adopts an attitude toward his lower self such as a person limited to the world of the senses adopts toward some instrument or vehicle that serves him.
Rudolf Steiner, How to Know Higher Worlds: A Modern Path of Initiation [Amazon, Bookshop, Publisher]