Zak's covering a lot of ground there, some of it a bit sketchily. At its broadest, the issue is that the Japanese tend to accept external reality as obdurate, something to be adapted to, even as they recognize that particular circumstances are endlessly shifting. One reason for that is the environment: Much of the country consists of near-impassable crags and gorges; a lot of the soil is poor for agriculture--we modern Western students, having been preached at about healthy Japanese eating habits are since we were little, are often shocked to learn in Japanese history classes about the poor food quality that was the rule until the Meiji Restoration--and natural resources are few. Even the closest trading partner is a sea journey away; for all intents and purposes, the Japanese Archipelago is at the edge of the world. It is also regularly visited by earthquakes, vulcanism, tidal waves, typhoons, and heavy snows.
Therefore, the Japanese have felt isolated and at the mercy of nature for pretty much the entire history of their civilization. I don't know that the way society evolved to value group affiliation, discipline, and emotional detachment was inevitable, but it was certainly understandable. Nature frequently took away things that people had let themselves get invested in; in those sorts of circumstances, one reasonable reaction is to avoid investing yourself in things and to find safety in numberswhiteperil