Just depressed

I'm just so fucking depressed right now, and I don't even know why!  It's like I crossed some invisible line in the sand. I don't want to do anything.  I'm just vegetating, taking up space at the moment.  I'm always tired, and can't seem to get enough sleep. Maybe it's the snow or lack of sunshine.  Maybe it's my wife's new non-sleeping habits.  Whatever it is, I just want my mood to improve. Sigh.