If I listened to my body, all I'd hear is "Woah! Woah! Woah! What the #$#% are you doing? Sit your @ss back down."
There's another "older" guy who I talk to and we often joke that the first 1/4 mile is the hardest. You never know what's gonna hurt today. After that you can find a pace and a route for that day. When I leave the driveway, I have no clue how fast or how far I'll run that day. Sometime, after a mile or two, I find I feel much better than I did when I started. Listen to your body.
