how would one be able to tell the difference when amped up on adrenaline or after having hit "the wall" at 30-35km during a long distance run? I've run ultras

how would one be able to tell the difference when amped up on adrenaline or after having hit "the wall" at 30-35km during a long distance run? I've run ultras before and not long ago crossed the Alps on foot with nothing but a tent and good cheer. The thing that would always make me stop is issues with slow-tissue (bones, joints etc). Not because "I feel this is the right think to do", but my body isn't leaving me any other choice. Ofc assuming the decision to stop or keep going isn't influenced by peer pressure. I've once come home with bleeding nipples (chafed by a new white Asics running top) so badly that it looked like I had been shot on the trail and the bleeding wouldn't even stop in the shower. It was pain far worse than a sprained ankle or broken leg. In your analogy I'd consider a sprained ankle "bad" pain while the chafed nips "good pain". Severity of pain might not be the most reliable indicator in mid-range pain levels. But it's always reliable when it dominates over a strong will. Basically you always know when you're _done_. Peer pressure is a dangerous cloud in judgement here which is why I hate doing these things competitively or with friends (one always ends up the sparing partner of the other).