Learning how your body works, how it responds, how to differentiate between different signals and form your own set of useful labels for them, all that forms the body of knowledge that makes the "old guy endurance" possible. I haven't yet met anybody who didn't do some of that learning the hard way, as the best move wasn't always the intuitive move.
I agree with both your points.
I don't know if I've written about this before here -- if so, forgive my repetition.
The winter after I graduated from college, I hiked the Napali Coast of Kaua'i. Eleven miles in, at Kalalau beach, there's a waterfall a couple of hundred meters inland. It's the best place to get fresh water, and the only place nearby to take a shower.
Kalalau, by the way, may be one of the most hauntingly beautiful places on Earth. I ended up staying several days after my food ran out, and, like two close friends I first met years afterwards, I had a freak accident while I was there that could have ended up killing me. I'd go back in a heart-beat; so, I suspect, would they.
One morning as I walked up the canyon leading to the falls, a herd of wild goats happened to be grazing in front of me. As I moved forward along the trail, they moved back, towards the cliff face at the head of the canyon.
This will be interesting, I thought.
When we got to the falls, I was amazed to watch the herd scramble up the sheer cliff walls. Then, as I watched, open-mouthed, one-by-one the goats lept across the face of the falls, unerringly finding a foothold on the opposite side. The athleticism and grace of their leaps took my breath away.
The last goat appeared to be old, or perhaps injured, as it was moving more stiffly that the others. As I watched, it reached the spot where the others had leapt, and it paused. It looked carefully at the narrow, thundering column of water in front of it. And then, very carefully, it stepped where the others had lept, unerringly finding a foothold on the opposite side.
That old goat knew it's stuff.
Before reading your comment, I hadn't occasion to remember that for some time. Mahalo.