Duncan's Tip o' the Week! TAKE A BREAK
I repeat this advice often, and always will.
Walk away.
Just walk away.
Like many other jobs, writing is often seen to be something you have to grind through. Something you can force if you just have the right work ethic. The right attitude.
But, force is not often conducive to creativity. Creativity is like water - try to slam it repeatedly and it can feel as hard as concrete. But, allow yourself to slow, to relax, and you'll slip right in.
The brain is very good at fixing things in your mind, circumventing writer's block, having revalations and epiphanies, when it's not being pushed.
So walk away.
If you have writer's block, if you're feeling tired, if you're sick of your work, if you can't write another word, just walk away. An hour, a few hours, a day, a few days - go do something totally different, and don't think about your work. Come back fresh and healthy and you'll likely find things that stumped you previously are revealed to be no more than a trifle to deal with.
Just don't leave it too long or you might start to forget crucial details. You don't need a year's break, you probably just need a few days. But you should experiment with what works best for you. Everyone is very different, after all.