Similarly, my last book was an emotional roller coaster and I thought I could get rocking on the next story, but I've been fighting it for months. I eventually realized that I needed some down time to regroup and recharge my emotional batteries, which is what I'm doing now. The book is about 3/4 complete but I need the break to finish. Especially as I'm getting anxious to start the next book in the series, #5.
I cut my author teeth writing romance. Most of my backlist is romance, but I moved away from the genre when I started writing thrillers (two pen names). Book #5 is a prequel and will actually include some romantic elements that have been missing in my thrillers...combining both of my writing loves. Crossing my fingers it works.
Anyway, never be afraid to take time away from writing, especially if the story was very emotional. It's called self care.