I think my own personal motivation for writing isn't 100% clear. I sometimes feel like I don't know who I am or where I'm going, and this quickly translated into my characters. While this might have been cathartic for me, it left my characters as spectators in their own lives, unable to understand themselves and dragged along by forces beyond their control.
Ironically, this is exactly the formula adopted by the TV series Mad Men, which has a whole cast of characters trapped by their own lack of self-awareness. This is all very nice and multi-award-winning, but Mad Men is not a children's adventure novel!
Some other TV writers (Aaron Sorkin and David Mamet, for instance) express writing entirely in motivational terms; the story has a protagonist who wants something and the antagonist must stop them them from getting it - right until the end of the narrative. I find this rather too reductive, but it's true that such clear motivations do add drive to the plot.
Although I did have some character motivation in draft 1 of Back from the Dead, it was spotty and unfocused. One of the secondary characters turned into a spotty and unfocused teenager, actually, spending much of the second half of the book in bed. Needless to say, this wasn't terribly dramatic!
The main character lurched from one crisis to another, and this series of separate motivations had the effect of constantly breaking the tension - which is the all-important element that keeps the reader turning pages. The trick was to give him a proper arc, some objective that kept him busy across the whole novel. In the first draft, he was trying to find out what happened to his brother, but spent much of the book under the (mistaken) impression that said brother was actually dead.
For the redraft, it was suggested to me that I have him look for his parents instead. So, out went the brother and in came Mum and Dad. For a while, I really didn't like this idea and it wasn't until I gave his parents some proper personalities and backstory that things began to snap into place. One of the unexpected side-effects was numerical - having two people to search for instead of one gave me twice the options. I could sideline one or the other and still keep the tension, or give my hero a headache by presenting him two different directions to go at the same time!
Once I had the hang of this character motivation lark, I found improved motivation for many of my secondary characters as well, including a much better drive for the main baddies. A lot of this happened quite organically as we worked on the plot and, to my mind, adds some satisfyingly crunchy layers to the story. This is the essence of producing multiple drafts, I think, taking a punchy story idea then adding depth and nuance.
I'm not sure if all this has done anything for my own motivational dilemma, but maybe all writers should retain an air of mystery. One thing that's become clear to me is that I should really love Mad Men, but I just can't get into it. It's just that bit too slow for my tastes - despite my clear ability to identify with Don Draper's ongoing existential crisis. It seems that with fiction - as in so many other things - what I really need is some serious drive and focus.