How does Judith Viorst use imagery in Necessary Losses?

Imagery:

"The potter who works with clay recognizes the limitations of his material," writes Margaret Mead; "He must temper it with a given amount of sand, glaze it thus, keep it at such and such a temperature, fire it at such a heat. But by recognizing the limitations of his material he does not limit the beauty of the shape that his artist's hand, grown wise in a tradition, informed by his own special vision of the world, can impose upon that clay." She is saying that freedom begins when we acknowledge what is possible - and what is not. She is saying that if we come to know the nature of our clay, we can impose our destiny on anatomy. (129)