One way to combat those rough patches is the ever-popular flash fiction writing prompt. Set your main work in progress aside for an hour or a day (or even a week in some cases) and write an assortment of very short stories (fewer than 1,000 words) inspired by random first lines. It loosens the brain muscles and gets your creative juices flowing.
While you can find about a billion prompts online, I've also included a few below.
1) I danced in pee.
2) And that's when I shot my grandmother. (Note: I was told I could not go the zombie route with this one, so I'm passing that on to you.)
3) The dragon was defective.
4) Timmy was allergic to bratwurst.
5) He didn't want to eat the soup.
6) They were all around me, and I had gas.
If you decide to write any flash fiction using these prompts, please leave your story in a comment. Thanks a bunch to my writing group for their inspiration and weird sense of humor.
For more prompts, check out these sites:
Writer's Digest Creative Writing Prompts
Daily Writing Tips
Prompt Generator (This one is actually for writing school essays, but it's still a nifty little tool.)
Poets & Writers Writing Prompts