I was thinking the same thing about the walk. "Crashing" is our first inclination after a hard day, but sometimes we just need to unwind mentally AND physically. Walking is easy and you can let your mind wander while you do it.
You could set your running shoes by the front door with a water bottle, and when you get home, go out for a walk... like Dance said, even just 15 minutes! You'll feel refreshed, and you'll feel good knowing that you've worked a bit of exercise into your day.
I actually went shopping after work today, so I ended up walking around for about an hour. So by the time I got home I was legitimately hungry !woohoo!
and made a reasonable dinner (two vegetables!)