Burnout sucks, and it can be hard to deal with. I began work on my startup in my spare time in college because it was fun. Once I jumped into it full time it turned my life on its head. After several months I was tired of working solely on my product, and I was tired of being at the computer in general. To gain perspective, I unplugged for a while. I read more books. I took up running again. I watched talks on TED.com and rediscovered movies and TV shows. Most importantly, I began coding stuff for fun again -- stuff that was totally not related to work. I felt guilty at first, but I ended up being far more productive in the long run.

It turns out it's the little things in life that keep you sane.

Are you a founder? Do you hold a significant amount of equity? If so, you have the power to chill out and take some time off. If not, you should remind your employers that you are a human being who will work reasonable hours. Maybe that means extending your deadlines; maybe it means they need additional developers to help handle the work. The bottom line is this: if you aren't being compensated the same as the founders then you should not be expected to have their level of dedication.