“The problem of meaning is created by limits, by being just this, by being merely this. The young feel this less strongly. Although they would agree, if they thought about it, that they will realize only some of the (feasible) possibilities before them, none of these various possibilities is yet excluded in their minds. The young live in each of the futures open to them. The poignancy of growing older does not lie in one’s particular path being less satisfying or good than it promised earlier to be — the path may turn out to be all one thought. It lies in traveling only one (or two, or three) of those paths. Economists speak of the opportunity cost of something as the value of the best alternative foregone for it. For adults, strangely, the opportunity cost of our lives appears to us to be the value of all the foregone alternatives summed together, not merely the best other one. When all the possibilities were yet still before us, it felt as if we would do them all.”
— Robert Nozick, Philosophical Explanations (1981)
Found through the blog "more than 95 theses"