Faith

She told me that faith is like a glass of water. When you're young, the glass is full, and it's easy to fill up. But the older you get, the bigger the glass gets, and the same amount of water doesn't fill the glass anymore. Periodically, the glass has to be refilled.

— Detective. What if I told you that God and the devil made a wager... a kind of standing bet for the souls of all mankind?
— I'd tell you to stay on your meds.
— Humor me! No direct contact with humans. That would be the rule! Just influence. See who would win.
— Okay, I'm humoring you. Why?
— Who knows. Maybe just for the fun of it. No telling!
— Oh, so it's fun. It's fun when a man beats his wife to death, when a mother drowns her baby. And you think the devil is responsible? People are evil, Mr. Constantine. So that's it.
— You're right. We're born capable of terrible things. Then sometimes something else comes along and gives us just the right nudge.
— Well, this has been real educational... but I don't believe in the devil.
— You should. He believes in you!

You may lose faith in us, but never in yourselves.