Need to figure out how to create an effective and compelling backstory? Read Melanie's explanation on Justification:
We all share the same basic psychology but how it gets “wound up” by experience determines how we see the world. Eventually we reach a point where we’ve had enough experience to arrive at a conclusion that things are always “that way” and to stop considering the issue. And that is how everything from “winning drive” to “prejudice” is formed – not by ill intents or a dull mind but by the fact that no two life experiences are the same.
The "wound up" determines the "wound" of your Main Character. Their justifications protect while simultaneously defending them against further emotional injury. Until, that is, something or someone shows up to shake things up:
Stories begin at that moment – when the Main Character’s long-held subconscious belief system, world view, philosophy, or template for behavior comes into conflict with the world around him or her. And the story’s structure is all about how an Influence Character repeatedly brings this conflict to the surface in one context after another until there is so much evidence that the Main Character’s view is incorrect, that he or she must make a choice in a leap of faith: Do I stick with my long-held beliefs, even though they don’t seem to be solving the problem, or do I switch to a new point of view that seems to explain things, yet has never been tried?