Practical experience. In a number of survival school, army, and other, scenarios, I found that there were always guys who “knew more”. They possessed every tool, novelty, gimmick, and piece of equipment that opened and shut, and they had read all of the books, and sometimes they were the fittest, and boy they were the first out of the gates. But they tended in the end, almost always, to be the first to get homesick, gippo guts, sun-stroke, hyperthermia, hypothermia, blisters, and whatever else – of any description, you care to name.
But the guys who had cheap shoes, less-expensive gym contracts – if any, had not watched survival programmes on cable TV, and who had never read a book on bush lore, but who had actually spent some time in the cold without an expensive jacket, had actually spent days and weeks in their childhoods getting bitten by mosquitos and stung by poison ivy, who had gone without as much water as they would have liked once or twice, and who knew what is was like to be in the dimness of a forest, or the emptiness of the savannah, tended to do better.
There are always exceptions, and sometimes genetics, willpower, physical fitness, and education, play magnificent roles, especially willpower(!), but generally-speaking there is no substitute for practical experience over YouTube videos.