I usually have a long to do list. I found that if I do something on the list, and then reward myself with something like a walk outside with the dogs, exercise on the treadmill, a chapter in a good book, or time on sparkpeople, I can work my way through much of my list without struggle.
I found a couple great apps for ipad that show great trails for running or biking or hiking as you work on the treadmill or stationary bike. And while I'm "running on the trail" I can listen to all my favorite music on Pandora. I want to get in my exercise!