There's not a good poet I know who has not at the beck and call of his memory a vast quantity of poetry that composes his mental library.
Poetry operates by hints and dark suggestions. It is full of secrets and hidden formulae, like a witch's brew.
A lot of the fun lies in trying to penetrate the mystery and this is best done by saying over the lines to yourself again and again, till they pass through the stage of sounding like nonsense, and finally return to a full sense that had at first escaped notice.