I can speak from my years of experience. New runners try to distract themselves from the pain. Loud music, head games anything to take the focus off the pain.
Seasoned runners focus on how the body feels. Us older runners get better and better at running through pain and discomfort. The brain tells the body when to stop when it feels damage is being done. With years of experience you learn to push through this limit and its no longer the perceived pain slowing you down as it is your body's physical limits stopping you.
I'm at the point where I can push myself to such limits in a race that it is actually risky healthwise. Other old guys are there also.