Christians love to talk about David and Goliath because it’s a clear-cut story with a hero and villian and it’s easy to make everything a Goliath — illness, depression, overeating, etc.
But remember this is a real story, not an metaphor. Most observers probably thought this shrimp David was going to get his head bashed in. So how did he do it? Here’s a short list:
He ran forward.
David took the initiative. Where others ran away, David moved forward. I’m sure this surprised Goliath a little. Of course he didn’t care too much whether this curly-haired guy ran or walked. But I think David gained the upper hand because he went on the offensive.