Almost any activity with a serious element of danger has a similar rule. The one I know that pilots say is "there are bold pilots, and there are old pilots, but there are no old bold pilots".

These endeavors have these sayings because they attract people who are willing to take risks, and all too often begin measuring themselves by how far they'll go. In the dive world, pairs of divers often die on dives that neither really wanted to do, but neither was willing to be the first to suggest cancelling.

We now see some of this in bicycling when people join clubs that have them "competing" with others via the internet. Who can make the fastest time on a descent, who has the most continuous streak of riding, and so on.

There's nothing wrong with competition with others or yourself, or setting goals and pushing your limits to reach them. OTOH when the desire to make a goal overrides the internal brakes we all have, we enter murky waters, and wind up trusting luck to separate heroes from victims.

So push your limits, but if you find yourself doing something only because not doing it means not meeting some sort of goal, the internal alarm should sound.