I've been in that same boat, being blessed with both bipolar and depression, and although just saying "hey some push-ups will do the trick" is perhaps a bit trivial I will add that even a tiny bit of exercise will help as it releases endorphins that are rather pleasant. Even on really fucking shitty days, I've tried to do a little work out. It's not a work out that will get me buff or anything but that's not the point. It honestly started as a healthy form of masochism for me...I loved the pain and it took my mind off everything else for a minute so I could focus on breathing and form. Even one or two push-ups, a long run...anything really...can help. It isn't a solution, but it's a relief and in the world of depression sometimes that's the difference between waking up tomorrow or punctuating a very short life.