What does the fortune teller mean by covering his mouth with his hand?

There are two reasons for covering your mouth with your hand: one is to control yourself and calm yourself down. The second is to cover yourself up and not let others know that you are lying.

When hiding facial expressions, it often causes hand movements. Covering your mouth with your hand is likely to subconsciously hide your inner thoughts. When you see such an action, you must weigh whether the other party's words are false or not.