answer:A big part of it is that we tend to overestimate the ability of external circumstances—people, things, places, situations, etc.—to provide satisfaction. This creates a “hedonic treadmill” dynamic: You strive after this or that because you imagine that this or that will quell your persistent sense that something is missing; but even when the object of desire is attained, after a brief period of respite the chronic dissatisfaction settles back in. So the elusive something/someone-that-will-fill-this-lack remains forever “out there”. The misperception at the root of all this is two-fold: first, that satisfaction is the result of getting the externals of your life just so and second, that you are separated from what you need to be contented. Beyond meeting the fundamental biological imperatives, externals can only provide temporary patches to the sense of lack. But because there is a temporary relief, the illusion that the key to eliminating longing altogether lies in getting the externals right is reinforced. Thus, the treadmill. The solution, though, lies inward: careful examination of that perpetually discontented self, forever isolated from what it wants. How real is that?