It could be that you need to take a break from writing - I know that if work gets me down, I'll have to take a few days break from writing, and there are other things which will screw up my creative processes, like emotional upsets and stress.

Are there little rituals you have when you write? Any music you like to listen to, snacks you'd eat, TV or films or books that inspire? People you would talk to?

You may just be putting too much strain on yourself - you can find your way back.