Sometimes you just have to get a story idea out of your head. It drives you crazy until you can't think of anything else including the writing projects in front of you that need to get done. What do you do? You put it on paper.
My editor/friend told me to stop and just begin writing. I didn't want to. I like to have things orderly and the creative mind doesn't work like that. So, I stopped writing the book I am far into and turned to another topic. I wrote and wrote. Seventeen pages later I was exhausted. Nothing came to me. I couldn't go any further. No more thoughts came to me. The next day I rattled out a couple of more pages but it seemed to solve the problem.
Now, I have the beginnings of another book waiting for the right moment for creativity to strike again. I'm back to the other books I'm working on.