Have you ever watched a goalkeeper defending the goal? He doesn't let the ball in just any old way.
Our mouth needs a goalkeeper too! His name is Discretion. Sometimes we feel like saying something mean, or a lie, or talking back to mom. If there's no goalkeeper, the "wrong ball" gets out of the mouth and scores an own goal (causes trouble).
Today's proverb says: "Be careful." Put a goalkeeper in your mouth to only let out words that are good, smart, and true.