Climbers have a saying that sounds like a contradiction until you look at the records: the summit is the halfway point.
On the highest peaks, accident reports show that most deaths happen on the way down rather than on the way up. The reasons are not mysterious. The hardest work is behind, the goal has been reached, and the attention that carried the climber up quietly lets go. Fatigue is at its worst. The weather has had all day to change. And the one thing that had been holding every decision together — we are still climbing — is gone.
Experienced parties answer this with a rule made before anybody sets off: a turnaround time. At that hour the party goes down, summit or no summit, and the decision is not revisited on the mountain, where tired people make generous arguments for carrying on.
The last stretch of any piece of work is where it is most often lost. The calculation is finished, the answer is on the page, and the mind is already somewhere else — which is precisely when the wrong line gets marked, the unit gets dropped, or a correct number answers a question nobody asked.
Thirty seconds, at the end, after the thinking is done. Not because the work was poor, but because that is where the descent begins.