One has to be careful how much we let our bios define a character. Obviously, we want to know enough about a character to help shape the story, and in that way, such details as Clarice's childhood tragedy are helpful to know in advance, as are broad character traits.

But we must also be careful not to overly detail a character in advance. Characters shouldn't be defined, locked-in constructs of our imaginations. They should be more organic than that. Rather than feeling like we are the omniscient God who created them and knows every thought and detail about them, we should be their biographer, inquiring about who they are, and sometimes not having a surefire answer.

The best character moments, in my experience, arise when characters surprise me as I'm writing them, revealing a detail I hadn't prepared for or saying something I didn't expect.