Why do we clap our hands? Think about it. You're watching a play; you're watching a movie; a ballgame. And when something good happens, you clap your hands almost reflexively. Why is that?
My theory? Kindergarten. Remember the song: "If you're happy and you know it, clap your hands..."
That's where we learned it! Why do you think when we're mad, we stomp our feet?
Just be thankful the song didn't go, "If you're happy and you know it, shit your pants..."