When we talk about a grandmother's love, we're talking about a particular kind of love...one that's over-the-top, a bit spoiling, and tremendously accepting and encouraging. When we say that no one loves you like grandma does, we're saying something about the QUALITY of that love. The Bible, and The Psalms in particular, are FULL of metaphors (like a grandmother's love). And Psalm 23 is the most famous of them all: God's care for us is LIKE that of a shepherd to his sheep.