Your opinion of yourself acts like a lens through which your experiencing passes. It is made out of carefully concealed beliefs each with a ready response to any flat out challenge and it runs by itself with no need for constant adjustment. When, in spite of this a passing injury is sustained your perception in its mental pole becomes distorted as if under the influence of a magnetic field. It is the distortion that leads to the belief that the centre of awareness is inside that core opinion you hold of yourself, or what is called egoity, in other words the identification of ego and self. The illusion is tightened in suffering and loosened in joy, but both constitute traps in their own ways which prevent the illusion from being overcome but simple disinterested observation.