stretching abstraction very far.... at any moment in time (say t), one could think of one's life as a cons pair of time gone by and the future.

such that:

(car life) -> past
(cdr life) -> future.

(cons past future) -> life

and now at the time t+1, one could recalculate life as
(cons (+ past 1) (- future 1))

if expected age is a constant *FULL-LIFE*, then in the beginning we are
(cons 0 *FULL-LIFE*)

and in the end
(cons *FULL-LIFE* 0)

and mid-life crisis is when
(eqlp (car life) (cdr life))