“When you write a poem, you discover that the very necessity of fitting your meaning into such and such a form requires you to search in your imagination for new meanings.”

Source: The Courage to Create (1975), Ch. 6 : On the Limits of Creativity, p. 119
Context: When you write a poem, you discover that the very necessity of fitting your meaning into such and such a form requires you to search in your imagination for new meanings. You reject certain ways of saying it; you select others, always trying to form the poem again. In your forming, you arrive at new and more profound meanings than you had even dreamed of. Form is not a mere lopping off of meaning that you don't have room to put into your poem; it is an aid to finding new meaning, a stimulus to condensing your meaning, to simplifying and purifying it, and to discovering on a more universal dimension the essence you wish to express.