This myth is mostly true–especially since God basically said the same thing in 2 Corinthians 9:7. The myth part lies in how we use that verse. The Apostle Paul tells us something specific about the character of God at the end of verse 7: he says God loves something. That’s a pretty big deal when the Bible spells something out so clearly and explicitly.
What does God love? A cheerful giver.
But what if I don’t give now, or I don’t give cheerfully? Should I wait? I think the opposite is true: the cure for not giving is giving. Just like the cure for a fear of dogs is to be around dogs, you will never conquer your materialism by keeping it close. You have to let it go.