We must begin by recognizing that as long as God is God and we are his creatures, there must be some unanswered prayers. This is because God keeps hidden his own wise plans for the future, and even though people pray, many events will not come about until the time that God has decreed.

I think it has some valid aspects to it, but I also think it breaks down. (Which doesn't mean it's a bad analogy, just a limited one. An analogy that is limited can still illustrate a valid point.)  

In my life, I’d already seen enough evil and suffering to feel deeply troubled by it. What I needed was to find perspective on what troubled me. In this process of writing If God Is Good, I’ve taken most pleasure in focusing closely on God, exploring his attributes of goodness, love, holiness, justice, patience, grace and mercy.