Justin recites some lines from the play Our Town to Via. (p.194) What one word sums up the theme in these lines?

I'm reciting: yes, the sun's come up over a thousand times. summers and winters have cracked the mountains a little bit more and the rains have brought down some of the dirt. some babies that weren't even born before have begun talking regular sentences already; and a number of people who thought they were right young and spry have noticed that they can't bound up a flight of stairs like they used to, without their heart fluttering a little...