Pushing yourself daily keeps you from negative and useless patterns of thought. Not just a cliché, running is good for you. Sure, maybe it's not the best for your joints but, getting your heart rate up for 20-30 minutes in the morning brings out a quantifiable increase in daily productivity. I'm not going to link you to some article that was the product of some scientific study. I will just challenge you to prove me wrong.
I will get on a role for about a week, running four or five times. My creativity and productivity, as well as focus seem to all work together. It is truly amazing. Then, I get complacent. It's the rebounder for 15 then 10 minutes. In a few days it's a lackluster free weight routine that lasts not nearly as long as it should and the next thing you know my drive for excellent work and creativity are in free fall.
So, I say run every day and feel great. Do your best in all you do so that when you look back on these days when you thought you were going no where, you realize you are in a great place because of the work you put in during hard times.