In our everyday life we can see that it is this sharpness of the ego, of "I", of "me", that hurts all the time, whether it be in someone closely related or not; whether it be son or daughter, father, mother, brother, sister, or just a friend. If anything about them hurts us it is just this ego. If one person hurts another it is only because of that person's ego. If we ever experience suffering in this world it is through this ego; sometimes it is the ego of another person, but sometimes it is our own ego too. One may compare it with a thorn which is always pricking: it hurts whoever touches it. The more egoistic a person is the more it hurts. So the teachers of mysticism know they must humiliate this ego, and the various methods they use are to do just this.