In Psalm 141:3 David prays: “Set a guard, O LORD over my mouth; keep watch over the door of my lips.”
We often think of prayers as being for God to protect US: “set a guard over me; protect me”, etc., and those are legitimate kinds of prayers. But it is notable that here David prays that the “guard” that God would set would be over his OWN MOUTH! Many of us would have to admit that we need to pray the same thing.

It is notable that many believe Psalm 141 to be an “evening prayer”, and :3 would certainly fit with that idea. It has all the feel of one who looks back on the day, and remembers with regret how he has said so many things he shouldn’t have. So in this “evening prayer” he penitently asks God to help him avoid such things the next day. It is a prayer that perhaps you need to pray: “Set a guard, O Lord, over my mouth …”.