In Graham Cole's book, God the Peacemaker, he quotes Blaise Pascal speaking on the paradoxical wonder that is every human being:
"What sort of freak then is man! How novel, how monstrous, how chaotic, how paradoxical, how prodigious! Judge of all things, feeble earthworm, repository of truth, sink of doubt and error, glory and refuse of the universe!"
Because all people are made in God's image, human beings are the glory of the universe and are capable of incredible things. But because of the Fall, humans are the garbage of the universe, with corruption and rottenness staining all we do. If we forget that man is in the image of God, we might be too pessimistic about humanity. But if we forget that man is fallen, we will surely be too optimistic.
Holding both truths seems to me to be the most healthy way to think about mankind. We are both the glory and garbage of the universe, a wonderful mystery indeed.
(By the way, for anyone interested in reading more about this, I'd recommend Anthony Hoekema's book, Created in God's Image.)