Here’s an interesting prompt: avoid starting from scratch. This constraint prohibits the creation of new raw material (e.g., writing into a blank document). You may only rewrite or edit existing text.
The result is much more consideration on what already exists. You scour your drafts, your existing work, and look for neglected ideas. You might realize how much polished work is ready for publishing, promotion, or a new purpose. If not, maybe you look outside of your body of work, and into somebody else’s—and find new opportunities to respond to or elaborate on (with proper credits, attribution, and citations of course).
When you feel like you don’t have enough time or energy, this prompt is particularly helpful.