Books, being the long and onerous journey that they are, often benefit from the break of shorter writing projects.
I've written about this before here. I'm a writer who benefits from an occasional pause to the slog of a book. Although I used to feel mildly guilty about this sidetrack into short stories or essays, I usually come away refreshed and ready to sink into the long haul again.
Right now, as I've also shared, two of my novels are making the rounds of contests and publishers. There's nothing I can do to accelerate or make the process more successful. So I'm distracting myself with short pieces.