One last quote that struck me as I read the rest of Poets on Poetry, a collection of essays edited by Howard Nemerov:
William Jay Smith: I have always believed in Jean Cocteau's dictum that the artist should find out what he can do and then do something else. The poet should always be venturing, trying out new things. One doesn't want experimentation for its own sake, the sense of the freakish doctor surrounded by retorts in the laboratory, but one does want the poet who is willing time after time to risk everything and play for the highest stakes. The poet must be constantly exploring, going out on a limb. This does not mean the continual development of wholly new styles, but rather the enlargement and expansion of one's basic style. It means putting out new shoots, growing as a tree grows up and out, feeding more and more on light and air.