I know this isn't really what you had in mind, but it's a cute one, and it reveals some of our excuses. My mother discovered it in a magazine (so I don't know the author), and I may not have remembered the entire thing.... Anyway:
Here's to him who early rises And goes through his exercises, Bending over, touching toes! I am never one of those - Some days I'm too hot or cold, Other mornings, just too old!
I think the "No Pain, No Gain" motto is useful only if we can teach the difference between (1) the good/pleasant ache of working muscles in the right way to push us beyond our limits and (2) actual pain which is designed to tell us that we did something wrong and harmful.
I like the "No Pain, Just Gain" motto.
This thread may inspire me to work on getting fit once again.