In four short lines, the speaker addresses his own hands with a firm command: do what you are told. The “balloon of the mind” is a wonderful image for a wandering, inflated, unmanageable thought or imagination. It “bellies and drags in the wind,” meaning it catches every breeze, pulls in different directions, and refuses to stay still. The speaker wants it brought “into its narrow shed”—a small, controlled space. The mood is one of tense self-discipline. There is effort here, even strain, as freedom and order pull against each other. The speaker seems to be trying to make unruly inspiration submit to shape, as a poet might force airy thoughts into the tight structure of a poem. The result is compact and a little stern, but also alive to how difficult that taming can be.
The Balloon of the Mind — Summary
Hands, do what you're bid; Bring the balloon of the mind That bellies and drags in the wind Into its narrow shed.