assorted apothegms

eventually
all sources of life are external,
all means of living internal.

pride is most pernicious
in those who are no longer trying
to live up to their potential.

(if you know what I'm talking about, consider yourself somewhat at risk).

one for the generalists:

the depth of a soul
is measured in the breadth of its interests
the breadth of a soul
in the depth of its insight

and, not really an apothegm...

in his later years, my grandfather became a very careful sort of scientist:
he was always repeating his observations.