I'm wedged on Worldwired, and I even know why. I'm wedged because the setup is done, and it's time for things to start changing in defined ways that involve moving the story forward to a massively complicated state that will collapse its wave-state into a satisfying conclusion when I pull the right string... and I don't know yet how the string needs to be threaded through the wave-state. I think it needs brain-time, because I need to develop the actiony part of the plot more (as opposed to the political, intellectual, and emotional conflicts, which I have going just fine, but I haven't quite established the physical threats) and I also need to understand where the antagonists are coming from, what they want, and what they're willing to do to stop the protagonists.
Brain-time always makes me feel guilty, because it's not actually writing, but it's a necessary part of the process.
So yes, I'm fortunate. Because I just physically can't write any further until this stuff has hammered itself out in my subconscious. And that's actually a good thing, although it used to make me panic before I understood my process. Because while I sometimes have to cut ten pages of my characters explaining the plot to me so that I understand it, I haven't yet had to cut two hundred pages of haring off in a direction that has nothing to do with the plot.
It's not writer's block, and it's not not being able to finish the book, and it's not that the book is failing or falling apart on me. It's just that it's time to pause and let the backbrain have at it and sort out how the actual structure of the book hangs around the shape of the story I have in my head.
My backbrain will figure it out. I have faith in my process. It hasn't let me down so far.