A human being would certainly not grow to be sixty, seventy or eighty years old if this longevity had no meaning for the species. The afternoon of human life must also have a significance of its own and cannot be merely a pitiful appendage to life’s morning.
The significance of the morning undoubtedly lies in the development of the individual, our entrenchment in the outer world, the propagation of our kind, and the care of our children. This is the obvious purpose of nature.
But when this purpose has been attained—and more than attained—shall the earning of money, the extension of conquests, and the expansion of life go steadily on beyond the bounds of all reason and sense?
Whoever carries over into the afternoon the law of the morning, or the natural aim, must pay for it with damage to his soul, just as surely as a growing youth who tries to carry over his childish egoism into adult life must pay for this mistake with social failure.
Carl Jung the Collected Works