I just had my birthday, and for the first time in a long time, I had a good one.   It's amazingly clear why, too: I just finished a project for my household that's been kicking my butt for the last nine years.  Even better, it turns out that, with a decent space in which to work and away from constant distractions, I actually WILL accomplish things, even without being paid to do it (or having some threat or deadline hanging over my head).  

So, it turns out that it's not so much that (as I've been fearing for a while) I'm just lazy or have no self-discipline; it's that when the environment I'm using is difficult enough, it saps a lot of my primary initiative and doesn't leave enough to actually do the work.  So if I can solve the environmental problems, I can get a lot done.

There's nothing quite like having what you thought was a weakness of character actually turn out to be an external problem for making you feel good about yourself and optimistic about the future.  I highly recommend it.