It strikes me that writing a poem is like creating a picture by painting only the shadows. What the poem references is impossible to recreate, so we write around it. To work, the poem must achieve a certain volume defined by the words and, to last, the shape it makes must have a kind of movement or tension. You could also say that making poems is like sculpting pots, only the poem is not the pot but the space inside.
Whatever the case, it's been a frustrating morning. Clay, paint, shadows, words -- all I know is nothing I've started on today is holding together, much less making any space worth sounding.