I agree with getting out of the house. For months now I've been taking my dogs on an hour walk each morning. Some days, particularly weekends, I won't want to do it, but after 10 minutes into it I feel great.

This goes inline with working out, but it's certainly harder to convince yourself to do 45 minutes of strenuous workout vs a nice long walk with your best friend(s). I figure, even if I'm sick, tired, and my body aches, I can always walk miles.