@Ganymede Ah, if we're going for inspirational slogans then this is my favorite.
A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.
Robert A. Heinlein made a damn good argument there. It's one of my all-time pet peeves when I pick up zealotry, and it happens a lot; my sister's yoga instructor scoffs at any other discipline, gym-bros of course swear by how much iron they can move around exclusively, runners only run, cyclists only cycle and so on.
There's no reason for any of that crap. People should do whatever it is that gets them off the couch and that's it; for example I find treadmills dreadfully boring but I can walk or hike for hours just because it's how I'm wired. Some folks like the social aspect of taking classes and revel in pilates or the such but others want things to be more under their control (if I want to go to the gym at 6 am I can).
What matters in the end is being more content and in better health. I want to lift but I also want to run up and down a full basketball court without my lungs giving out. I want to be flexible and not feel like my hip hinge is made of rusty iron, and be confident I can pick a pencil from the floor without my lower back's nerves simultaneously exploding. And yes, I want to look good without a shirt on.
All of those things are important to me, not just one of them. But also any one of them is better than vegging out in front of the TV.