My motivation seems to exist in inverse proportion to the closeness to completion of the figure. Crap, not even had a drink yet

Motivation decreases as figure nears completion. That's better! Which leads me to consider that my primary motivation may be my imagination, as I look at a raw mini & think of how it could look if I do a world class paint job on it.
Of course it has nothing to do with reality; force effects & sparkles & flickering lights & shifting colour schemes & sound effects & smells are all part of the daydream. So the longer I paint it the more mundane it becomes and down the pan goes enthusiasm. Not for painting mind, just that particular mini, I'll happily embark on something new. Helps to explain my Eternal-WIP-Pile-Of-Doom and the grand total of 4 entries in my Gallery, 2 of which are Snotlings I zipped off as a break from minis that still aren't completed
Other reasons include the fact that it's the only one of my hobbies that really involves producing anything other than collections & catalogues. Actually DMing a game is creative too but is rather more ephemeral. As Friar mentioned, it's a nice distraction from the lurkier of my thoughts. I never used to understand, as a kid, how my mother could sit & knit/sew through a film on TV (after always, always missing the first 5 minutes) rather than actually watching it. Now I'll quite happily paint my way through a DVD box set. As long as it's well written, it works. Strange looking up from time to time to see something new in a scene I've "watched" multiple times, particularly when it's a knowing glance or signpost that I'd been oblivious to. I just think of it as getting better value! (I've also come to really value a good director/cast commentary, some are bloody awful. Joss Whedon still the best so far but Peter Jackson is edging a close 2nd).
Aha, back to motivation

I have a mountain of unpainted & WIP minis & I keep buying more. Must paint to justify that expense! And then you lot on CMON keep producing fascinating & inspirational work, so that gets me going too. CMOn again for the final one but it's my WIP thread here, my online presence is minimal so it's as close to a blog/website/facespace page as I'm likely to ever get. It's nice to update it now the initial trepidation has worn off
Cheers guys, B.