I read this on QueryTracker and thought it was good:
Great stories, and history for that matter, all hinge on change. The story isn’t in it when everything’s balanced and peaceful. That’s the end–or the beginning–of the story. The story is about the change that happens, that upsets the balance, and requires the characters to act, to respond, to live, and to change. That’s what a good story’s all about: taking a character and a set of circumstances, knocking them off their feet, and watching to see what happens.