Yes, force yourself to do things that you used to enjoy. That's what I do, although I'm a bit of a hypocrite as I don't do it as much as I should. I'd much rather take a sleeping pill and crawl into bed. I know it's counterproductive, but sometimes I just can't help myself.

When I was in college I would get incredibly depressed. I mad myself go to a free aerobics class 5 days a week of which helped. I also found a workout buddy, someone who would drag my sorry bum out of bed and force me to go to aerobics. I hated it, but always felt better afterwards.