One thought is circumscribed

One thought is circumscribed in fourteen lines.
One hundred forty syllables is all
You have to spend.  The whetting stone that grinds
The words is sharp: be careful now, don't fall

Behind and leave the stone with nothing there
To grind.  The more you write, the more you slow,
The more you pause to fit the space, for where
You search is empty now, six lines to go.

The mind was full of words not long ago.
You grabbed for sound and meaning, profligate
And spendthrift both.  You wrap it up, forego
The choicest words, admit it's second rate.

You'll write another poem soon I bet.
But aren't you glad to know this one is set.