Is it 21 days to make a habit? That would be a good start to a novel if one wrote every day. It is a crazy thing to actually do it. To think that the stories in one's head can overcome the long odds of the internal filter to land on the page organic and real and worthwhile. Longer odds to think others might like them. I encourage every one to pick some thing that might seem crazy or just not a dignified use of your "grown up" professional time and run with it. For 21 days. After that you can stop. If you still want to....
ER doc, army doc, busy mom, dog walker, author of ROOM FOUR, working on a sequel and an unrelated screenplay...