If You Understand the Phrase "Sensing Changes in Your Hair and Nails," Let Me Know

Here's a new poem by a former poet laureate:

On the Nature of Understanding

By Kay Ryan

Say you hoped to
tame something
wild and stayed
calm and inched up
day by day. Or even
not tame it but
meet it halfway.
Things went along.
You made progress,
understanding
it would be a
lengthy process,
sensing changes
in your hair and
nails. So it's
strange when it
attacks: you though
you had a deal