I've heard and used that quote many times, and they're words to live by.
I also like: "Anyone can workout for an hour. Its's the control of what goes on your plate the other 23 that matter."
Humans are visual learners and we see the fit/healthy people in the gym or out running. Consequently, we assume that's what it takes to get in shape. Instead, it's where we don't see them that it matters most: fast food restaurants, buying candy, or buying junk food.