All of a sudden, I sort of started to feel that I was constrained by the characters as opposed to enjoying them. And that remains for me to this day the line that I know where it's like, OK, you're not writing fan fiction anymore.
You can actually muck with history and think about what if, why not. What if there were dragons in the Incan Empire that allowed them to resist colonization? What if there were a massive dragon empire in the middle of the interior of southern Africa that decided to take objection to the slave trade?