I believe it was through the long poems I've been reading in On Extended Wings, that stevens was able to discover his strengths. Stevens talks about the poets subject, and how it provokes his sense of the world. A man's sense of the world dictates his subjects to him, and this sense is derived from his personality. And his personality manifests itself from the poets style.
On Extended Wings has pointed out how stevens resorts to words of uncertainty, or "skeptical music" in his poetry. In reading any of the poems in Harmonium, we see may, might, must, could, should and would resolve his poems. As if using the present tense would imply succesfull action, and it can be performed again with succeful action. Ive discovered this sense of "openendness" in his poetry, as if something or someone is searching for something in a lucid dream without direction. Perhaps stevens doesnt want his poetry the the reader what will happen and how it happen yet leave that up to the reader to interpret.