These methods are things that human beings discover again and again when in extreme pain or stress, and can be resorted to in like circumstances once learned. We read about them not only in philosophical texts, but in religious texts, biography, autobiography, and works of fiction, (Matterhorn being a case in point).
In Matterhorn, the example is a character nicknamed "Hippy" He has very bad case of "immersion foot" (aka "trench foot"). Yet, he had no choice but to tolerate it during Bravo Company's long hump through the jungle to an objective that had to be met in an impossibly brief period of time, with no food or water resupply for days. The pain he endures is incredible, the smell of his feet nauseating. How did he manage to walk on two badly distended and painful feet? From the book:
Hippy kept thinking of the girl who had first told him about meditating one night when he was on liberty from Camp Pendleton. He tried to concentrate on the now of the pain. She had told him that if he was uncomfortable on his knees in meditation, it was only because he was thinking about the time stretching before him. "Are you able to stand it now?" she had asked him. "Yes," he replied. "And now?" "Yes" he had replied again. And now the pain of putting his foot down hit him, but he could stand it. And now, on the other foot, but again, he could survive. And now. And now. The hunger was nothing.And later..
Hippy's feet grew worse. He took his bootlaces off to accommodate the swelling. He looked like a sleepwalker. He would murmur to himself, "Can you take this step now?" and then take the step. He repeated this procedure hour after hour, a spirit carried by crippled feet.By focusing on the moment, Hippy is able to endure that one moment. By doing this the next moment, he is able to endure that moment. If he thinks about the future, something that he has no control over, because it is out of the grasp of the moment so to speak, he becomes prone to distress and thoughts that he cannot endure.
So, we have an interesting admixture, one element of which is Stoicism's remonstrances that we should be very aware of the distinction between those things we can control, and those we cannot, focusing only on those things we can control, that is, basically, our attitude toward our situation (whatever it may be). If we can discipline ourselves to do this and ask questions very like those Hippy asks, we will be subject to less perturbation.
The other element is a sort of 60s era Zen Buddhist, Baba Ram Das Transcendental Meditation inspired ingredient, the "be here now" aspect of the girl's advice. By focusing only upon the single and momentary portion of our life that we presently inhabit (attitudes toward which being the only things over which we can honestly say we have complete control) we can endure, if we do this serially, for each successive moment, where, if we focus on the future, we cannot, or are less likely to succeed. We are more prone to perterbation.
Admiral Stockdale says as much in his accounts of survival in Hao Lo. Men that looked to the future, either with pessimism or optimism, were more prone to distress. If, on the other hand, one focused on enduring, one day at a time, to use the well worn cliche, one was better off.