When that happens I have to do a mental inventory and ask myself, "Am I better off finishing the run or should I just bag it and take tomorrow off?" Two things; firstly every run hurts a little bit - especially the first mile. I usually get into a groove and sometimes, very rarely, I really have gotten to that place where I'm feeling no pain and a run seems like less effort then a walk - mostly though the nice part of a run has an undeniable unpleasantness bound up with it. I like being able to go out for a run though so I put up with the bad. Second thing. I'm an unreliable source. For all the reasons I just talked about I don't trust my ability to take stock of my physical state. I do occasionally take off or skip for days at a stretch but it's like candy - I don't trust it because I like it so.
Here's the thing. If I get that balance wrong I end up walking in the middle of my run.
I imagine Honnold has to do that same self assessment. If he gets it wrong he plunges to his death. Which - to my mind - is totally crazy. Takes all kinds though.