I was just reading this morning about how the brain works. If you aren't learning new stuff, getting fresh input for your brain, it can have bad effects in the long run. I cited the factoid in a blog entry I write for the TechNotes blog, which I write for a non-profit education association I've been a member since I was in my 20s. Fortunately, I've been writing about new things for a long time.
The most apt metaphor for writing might not be the dried up oasis that needs someone to punch through the crusty dried sand overlaying the point of exit. It's the rusty water pump, that you have to work hard to get water flowing. It's the faucet in a farm kitchen overlooking the plain of verdant crops on a hot sunny day, spouting red water in spurts, like an old man with prostate problems.
When I need to write as a professional, it's amazing how many time I need to crank the water pump handle, let the rusty water run, until the good stuff shows up. What fun!