Short Answer:There are too many unpredictables or “known unknowns” and “unknown unknowns”
This reminds me of another great poem by Cavafy called Nero’s deadline
Nero wasn’t worried at all when he heard
the utterance of the Delphic Oracle:
“Beware the age of seventy-three.”
Plenty of time to enjoy himself still.
He’s thirty. The deadline
the god has given him is quite enough
to cope with future dangers.Now, a little tired, he’ll return to Rome—
but wonderfully tired from that journey
devoted entirely to pleasure:
theatres, garden-parties, stadiums…
evenings in the cities of Achaia…
and, above all, the sensual delight of naked bodies…So much for Nero. And in Spain Galba
secretly musters and drills his army—
Galba, the old man in his seventy-third year.