I've figured something out about writing, or non-writing, rather. If you've ever had writer's block due to stress, change of routine, then I have a few suggestions to get you back in the groove again. First of all, try not to panic. You've written before and it will happen again. I think the best tip to getting back into your work is to go over your old work. Edit the chapters leading into your new section. Believe me, even areas you thought were finished will yield some edit-worthy mistakes. And it will help set your mind to writing mode again.
Other suggestions are to listen to music related to certain projects—create a playlist. Take walks. Drink tons of water. Do a lot of water based chores like washing dishes, laundry, watering the plants. Of course, a good shower is the best thing ever for writer's block. It makes the ideas flow! I can't tell you how many times I've had story ideas, dialogue, plot fixes . . . while shampooing my hair. It's awesome, if not a bit inconvenient.
Also, don't pander to yourself about writer's block. If you can't write on a manuscript then write a blog, or a journal, or something, anything. It doesn't matter what you write, just write.
Sometimes I think we are afraid we can't match our former brilliance, that the magic has passed on to some other person. We will and it hasn't. Just keep repeating that to yourself. We will and it hasn't.