In her wonderful book A Poetry Handbook: A Prose Guide to Understanding and Writing Poetry, Mary Oliver makes the following obervation about poetry:
"Poetry is a river; many voices travel in it; poem after poem moves along in the exciting crests and falls of the river waves. None is timeless; each arrives in an historical context; almost everything, in the end, passes. But the desire to make a poem, and the world's willingness to receive it--indeed the world's need of it--never passes.
If it is all poetry, and not just one's own accomplishment, that carries one from this green and mortal world--that lifts the latch and gives a glimpse into a greater paradise--then perhaps one has the sensibility: a gratitude apart from authorship, a fervor and desire beyond the margins of the self."
A Poetry Handbook: A Prose Guide to Understanding and Writing Poetry