Positive reinforcement. Telling the kids they're doing well and to keep going. Dishing out praise when it's needed is important as it lets the students know that they're doing well. Some of my (all too) often repeated phrases include "well done", "nice work" and "good job!"
Alas, this poor kid has mixed up "good job" with "good gob". Gob is UK slang word for "mouth". As in "you've got a big mouth!" Perhaps he is giving me a subtle hint about something. I wonder.