I had to smile to myself when I read your initial post. This is how I feel almost every turkey season. By the end of the four week season I am tired. I manage to take a turkey every year, but after a month of getting up between 3-4am to go out and hunt 5 days a week, I get tired. Then I start saying things like I am going to give up turkey hunting. My co-workers laugh at me now because they know every April I will be getting all excited to hit the woods.
So don't worry, the spark will return. You just need a little rest.