NaNoWriMo Tip #3: This Time, It's Personal

But wait!, some of you who read my Tip #2 on motivation might be saying, My protagonist doesn't really have an internal motivation in the book, nor does he need one.

The reason he's on the journey is because he's a __________ (detective/cop/superhero/ninja/monk) and it's his ________ (job/duty/moral obligation/hobby/religion).

I'd see your point--that a detective takes a case just because he's a detective, and taking cases is what detectives do, and that because of this, he doesn't need any more personal or internal motivation in the story--but you'd be wrong.

There has to be something personally at stake for the character for this particular case, different from the case just before or just after. Otherwise, why aren't we reading about the case just before or just after? The reason we're reading about this one as opposed to that one is that this one is meaningful to the detective in some way. He can't just decide to return the money and quit the case and go to a bar...in other words, he can't simply be able to quit the novel. There must be some compelling reason--some personal interest and motivation--that keeps him there.