It occurred to me this morning:
The difference between the average runner and a marathon runner is that on off days the average runner is off, but the marathon runner only runs five miles.
By the way, I'm still in the first group, but trying to get to the second. This little quip occurred to me while running in the rain this morning and hating every minute of it. I usually find running to be very enjoyable, but today I just felt off and every step seemed to take a monumental effort. Anyway, since my goal is to be run a marathon, I figured I'd better forge on.
I think this anecdote is more generally applicable, imagine if you got "five miles worth" done on your off days in other aspects of life too. How great would your "on" days be!