I know what it's like. When I was only riding (and I am a cold weather wuss), I hibernated because I was used to sunny SoCal. I get tired, irrational (uh, sometimes!), and things that normally wouldn't bother me, bother me.

I agree with taking up new hobbies but I also think getting out is a good thing, if you can. Winter sports, running (if it's not icy out), etc. I actually just read a review of these clip things that go on your shoes for running in snow/ice. For me, if I can't exercise, I get strange and borderline depressed.

I'd also say to not be too hard on yourself. If there's a lot going on in your life AND it's winter, it's a bigtime double whammy. It will pass...just keep reminding yourself of that.