I just realised. It's resolutely winter, and I have SAD. It's been grey and pissing it down all week - I don't think I've even seen the sun since Saturday.
Duh! No wonder I have to lie in front of the lightbox for almost an hour before I can actually face moving in the morning!
Next newsflash: h-l discovers that the house is warmer when she remembers to put the heating on.