Okay, so this isn't exactly writing related, but it is something you can do while waiting for your muse.
While sitting at your desk, lift your right foot off the floor and make clockwise circles. While doing this, draw the number '6' in the air with your right hand. Your foot will change direction. Seriously, it will!
If you're like me, you'll keep trying this over and over to see if you can outsmart your foot, but you can't; it's preprogrammed in your brain. This info is supposedly from an orthopedic surgeon. Now, get back to writing.