They cannot always control what they say and do. Don't sit down and don't stop moving. Close proximity allows behavioral correction without negative verbal comments. Use your facial expressions and eye contact to convey your meaning. Students tend to pay more attention to what you do rather than what you say.
Teachers are great actors.
Your facial expressions and eye contact can convey tremendous approval. Children are sensitive to non-verbal gestures and you can use the positive ones to your advantage while building the esteem of the student. If needed, you should take a time out. I'm going to flash a work or phrase to you. See if you can write it down when I say go.