one precaution is necessary, failing which it were better to leave untrodden all steps on the path to higher knowledge. It is necessary that the student should lose none of his qualities as a good and noble man, or his receptivity for all physical reality. Indeed, throughout his training he must continually increase his moral strength, his inner purity, and his power of observation.
Rudolf Steiner, How to Know Higher Worlds [Bookshop, Amazon, Publisher]