An excerpt from The Mind: Its Projections and Multiple Facets by Yogi Bhajan (page 1).
I want to talk to you about your most important companion and its structure, the mind. Every human being who wants to excel and to develop the character and caliber that upholds the values of the soul needs a direct, fundamental relationship to the mind. you must have a basic practical understanding of the mind's conception, properties, Aspects, Projections, and 81 Facets. This is the minimum requirement to develop human sensitivity. So prepare yourself for an intense study. Not an intellectual debate, but an intelligent confrontation with your own experience.