Get out of the situation NOW, before the damage is too big to handle. Take a week break and go somewhere far from email and phone, and use the time to think how to restructure your work so it doesn't happen again when you get back. You need serious restructuring and lots of delegation. Nothing is more important than your well-being, and your company will suffer more in the long run, if you're down.

Daily exercise helped me, try getting your pulse up, if you do this regularly you will get much better mood, more energy and things will lighten up.