And if you aren't, get some more sun, by your comments, your body is probably wanting a shift into earlier hours? Get up early and hear the birds chirping without having to rush into an office. I think the same thing happened to me from 28-ish to 31-ish. I went back to school and finally entered the game industry and focused on less, just being good at that. Is there a field you want to get into that you haven't really tried? Just do it, start now in small goals.
Also, set some lower goals for yourself in smaller tasks and get them done quickly. Sometimes you are tied to bigger projects that make the rush of accomplishment numbed from the pain of larger projects if they are longer and less driven by smaller accomplishments/releases. Control some of these on your own.
Also, play some Red Dead Redemption or your video game of choice. They can really help reduce stress and provide escapes to clear your head after a day of work or when you need to shift to relax.