Please swap “poem” for “essay” or any other piece of writing:
Lucky accidents seldom happen to writers who don’t work. You will find that you may rewrite and rewrite a poem and it never seems quite right. Then a much better poem may come rather fast and you wonder why you bothered with all that work on the earlier poem. Actually, the hard work you do on one poem is put in on all poems. The hard work on the first poem is responsible for the sudden ease of the second. If you just sit around waiting for the easy ones, nothing will come. Get to work.