Oddly enough, my favorite answer to this question doesn't exactly come from the Bible. It comes from a Playstation game called Xenogears. A few of the game's characters have entered a cathedral, and they see two statues -- one-winged angels reaching out to each other. The Holy Mother explains the meaning of the statues in the context of her church's teachings:
Margie: Did you notice that the two great angels only have one wing each...? According to a legend handed down in Nisan, God could have created humans perfectly... But then, humans would not have helped each other... So that is what these great single-winged angels symbolizes... In order to fly, they are dependant on one another.
Citan: Ah, so that is the reason for it. I see... On further inspection, the left angel looks somewhat masculine... while the right one looks somewhat feminine. Now that is an unusual feature, is it not? Usually these depictions are not gender-specific. But these angels are clearly distinguishable as having opposing genders. And the space between them is the path from where God advents... Or could it be the path leading to God? Well... I do not know, it could be either, or even both. ...Now I see! This all coincides with the teachings of Nisan.
Margie: Ha, ha, ha! Why Doctor Citan Uzuki! You are an amusing fellow!
Citan: Oh! Excuse me. It is a habit of mine...
Fei: The doc knows a lot about a lot of things... Sometimes I can't even understand what he's talking about...
Bart: ...Hah! Forcing them to fly together...? It would be less bothersome if they could fly on their own, don't you think, Fei?
Margie: Bart! You miss the deeper meaning and beauty of it. Someday I wish I could be of help to someone like that.
That's why I think bad things happen. They help us learn to love, and to be grateful for our blessings. And of course, there's always the old saying that what doesn't kill us makes us stronger. *g*
Obviously, I haven't stopped believing in God.
~Rochelle.