The Couple by Louis Jenkins

They no longer sleep quite as well as they did
when they were younger. He lies awake thinking
of things that happened years ago, turning
uncomfortably from time to time, pulling on the
blankets. She worries about money. First one
and then the other is awake during the night,
in shifts as if keeping watch, though they can’t
see very much in the dark and it’s quiet. They
are sentries at some outpost, an abandoned fort
somewhere in the middle of the Great Plains
where only the wind is a regular visitor. Each
stands guard in the wilderness of an imagined
life in which the other sleeps untroubled.

(via today’s Writer’s Almanac)