Nothing on that list. I stop when I'm done. I never ride randomly. Every ride has a goal.
I remember one ride I had to bail from a couple years ago. I had come down with PMR, though it hadn't been diagnosed yet. My power suddenly disappeared after the first 1500' climb and descent and I knew I'd never make it up the 3000' climb in front of me, not captaining our tandem I wouldn't. Other than that, I can't remember a DNF. I have had to stop and take brief rests, but that's not the same as giving up.
If one intends to do something, it's a good idea to train oneself so that accomplishing that goal is doable. From then on it is, as they say, "between your ears." I can clearly remember a few instances when I really, really, really wanted an intervention. That's a good time to stop and eat something, have a drink. and then get back on the bike. Those are times when I learned that I could just keep on doing it anyway.
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Results matter