Can't See the Forest for the Trees

I didn't understand that expression when I was younger. "You can't see the forest for the trees." What does that mean, I wondered?

I understand now. When someone can't see what is right in front of them, when they aren't able to determine the importance of what is being said, or won't hear what is really being spoken. They can't see the forest. They only see trees. They see the specifics, but not the heart of the issue.

No amount of explaining will help them see otherwise.