What is this bible story called?

I'm pretty sure this story is from the bible. It's about a man who walks on a beach and in the sand he always sees his footprints and another pair, God's. One day he's tired and in pain and he only sees one pair of foot steps and he asks God why he wasn't there for him, and God says "When you needed me I carried you." Does anyone know what its called and whether or not its from the bible and where I can find it? Its one of my favorite stories. Thanks so much!