Exercise. It gives you energy and takes your mind of things for a while. We're not meant to sit on our buts in front of a screen all day. I know it's hard when you're tired and overworked, but it's indispensible. Also, sleep and eat well.
It doesn't have to be really physical: for me simple things such as walking in the nature for a while help a lot.
I also started yoga last year, and it has changed dramatically how I feel (no more back/neck pain, more focused etc). I'm actually increasing yoga to 2.5 hours per week now.