By the time John Young was walking around in the Descartes region of the Moon, he was an experienced and accomplished space explorer. He had lived and worked in space on three previous missions: Gemini 3, Gemini 10, and Apollo 10. With his background, he and Charlie Duke would have a shot at performing as flawless a mission as was possible. Well they did; and he did; and John even went on to later fly two demanding space shuttle flights. His record in space is unequalled.
But that is not where he made his greatest contribution, in space, that is. In my opinion it was on the ground, in the work of developing our spaceships, where John´s unique point of view made the most difference. John had an uncanny knack for spotting a flaw or danger or potential trouble spot in the hardware, the software or our operational procedures and techniques.
He not only could see what many of us could not early on, but he would then take it upon himself to get the NASA bureaucracy to understand and address the issue. This was not quick or easy, but John would hold on like a bulldog (he earned a B.S. in aeronautical engineering from Georgia Tech) until NASA would make the changes necessary to fix the problem.
John Young was one of the most effective engineering astrounauts that I worked with during my 18 years at NASA. I suspect he may have saved a few of our lives along the way.