Remember when @faithellis mentioned Dave's fuzzy brain? My buddy Steve had that exact thing happen after he quit his lunchtime runs. He said his afternoon meetings felt like wading through mud until he forced himself back out, even just for a ten minute walk. The fog lifted almost right away.
My friend Dave who does graphic design swears by his lunchtime walks. Said his work got all fuzzy when he stopped, but clearing his head outside fixed it. How do you get back on track after skipping a few days?