I agree about growing weary about life is a noticeable trend, among the older relatives I know. Still, human beings are remarkably different. Some are driven by a single overwhelming emotion, like curiosity. To these, I can relate.

Observing different people in my vicinity, I can't help but wonder: why are they so different? Some are energetic, others are not, some are athletic, others are not. Some age faster, others age slower. I can't help but notice that there is some large heritable factor to it, and it waits to be discovered and studied in its fullness.