Besides the obvious answer of doing what I love, I'd say equity. Given that there's very little of that in real life, I love having the ability to create it in my novels. For the most part, the "bad guys" get punished, the "good guys" prevail, and I'm a happy camper. Occasionally it doesn't happen that way, but that's the book's decision, not mine. I'd always choose to go for the happy, satisfying ending.