Since only one day in seven is for writing, the unused creativity accumulates, and interferes with sleep.
A former religion of mine used to frown on fiction or any make believe. Tried to be obedient, but when the dreams piled up, things got so bad they took over. Not joking. My mind was held hostage by an old man (why old?) with a reel to reel film projector. He forced me to watch, playing the same dream over and over, whether I tried to sleep or work. I knew I'd have to write down what I saw or die from exhaustion.
Then he went away, quiet as you like. And I never got the chance to thank him.