like the chest of someone sleeping

We lie back to back. Curtains
lift and fall,
like the chest of someone sleeping.
Wind moves the leaves of the box elder;
they show their light undersides,
turning all at once
like a school of fish.
Suddenly I understand that I am happy.
For months this feeling
has been coming closer, stopping
for short visits, like a timid suitor.
[Jane Kenyon, 'The Suitor']