Simply put, Sense of Self is our own Self Image. A character may not truly know who he is but he always knows who he thinks he is. This inward-looking view may be right on the mark or not even close. The difficulty a character has is that from inside himself it is impossible to be sure who he is. All he can do is take clues from the reaction of those around him. Interesting storytelling sometimes places a character among those who provide a warped feedback that creates a false Sense of Self in the character. This erroneous image may be far better, far worse, or simply different than his actual state of being. Other stories force a character to come to grips with the fact that he is wrong about himself, and the opinions of others are accurate.