When you're feeling low, grumpy, or even a little depressed, what do you want to do? The answer for most of us is not very much. Our natural response to a bad mood is to hunker down with our comfort of choice and hibernate a bit. 

But according to fascinating new -- and, sadly, very topical -- science, the best way to fight off the doldrums is to force yourself to get out there and do something new. You might have to drag yourself off the couch today, but this research shows you'll be happier for the effort tomorrow.