October Novel Prep Challenge

While doing the protagonist bio, a while ago, I began writing about her deepest darkest secret, which is making a whole lot of stuff clearer. It is a good idea to focus on the deepest, darkest secret for a while, which the character doesn't talk about or is even afraid of thinking of it. That opens to so many ideas, especially if the general story is character-driven.

Does anybody have similar or different ideas for character-driven storylines?