So why do we lie? Sometimes, it's done to embellish the story about the fish that got away. Sometimes it's intended to shelter someone who would be hurt by the truth (i.e., "Yes, Virginia, there is a Santa Claus.")
Maybe you are confident that you are a terrific lie detector -- you are sure you can separate the trustworthy from the slime. Surprise! More than a dozen studies have shown that there is no link between confidence and skill.