Here is what Stephen Spender says on T.S. Eliot:
"What is immediately striking about the poetry of T.S. Eliot is the difference between the work of the early, middle, and late periods. It is not just that Eliot never repeated himself and that he wrote a new poem only when he had something new to say and a new way of saying it, but that, at successive stages of his development, the poetry seems to proceed from a different consciousness." (T.S. Eliot, 3)
This itself is striking. Is it ever possible that one never repeat oneself? How does he know before he actually writes that he has found something new to say?