Creating and Leaving Out the Back-story

My novel, Lifters, is about a young woman mercantile detective in Seattle circa 1908. Spending the better part of four years getting into her head as a writer really helped me get into character as an actor. As you fiction writers know, you have to create a history for your character that brings the character to life for yourself.  But you have to resist the temptation to cram all that back-story into your novel.   parts of the character that never make it into the story. Something similar happens when you are acting.  The script is the starting point for your character.  Your imagination and life experience let you grow an imagined life from your character's lines.  You draw from this imagined life to enrich the character you are playing.  But you cannot go beyond the script.  As a novelist, you have to impose your own script on your story.