A poem begins with a lump in the throat; a homesickness or a love sickness. It is a reaching-out toward expression; an effort to find fulfillment. A complete poem is one where an emotion has found its thought and the thought has found words.
Robert FrostBefore I built a wall I'd ask to know What I was walling in or walling out, And to whom I was like to give offence. Something there is that doesn't love a wall, That wants it down.
Robert Frost