I have become extremely dependent on exercise in sobriety to regulate my moods. I know it's a substitute addiction but at least it's relatively healthy.
If you've skipped the gym a few days in a row and are feeling lousy, I'd suggest forcing yourself back in there. It may help lift your mood.
I'm at the point that I'm climbing the walls if I go more than 24 hours without exercise. That's when I get myself wound up on fruitless ruminating and depressing thoughts.