I'm a little worried about losing energy, but there are a few things that are clearly wrong at this stage in the first draft (I mean, it's clean and readable, it's probably even publishable, but it's not the best it can be, or the best I can do), and I think now is the time to go back and really think it through and fix it, before going on.
I am rather dreading starting revision. It's so easy to lose energy here, when you're looking at the muck you've created and wondering how best to dig it out. Like that bit of the basement where you've been throwing random stuff all year, and now it's time to clean it out properly. But I think it's for the best. Take your medicine, Mary Anne. The book will be better for it.