Simplify the following text for a Grade 9 native English-speaking person.
Original: In `` Sokka 's Master '' ( the 4th episode of third season ) Sokka expresses self-doubt and worry that he is not usefull as much to the group as his bender companions are .
Simplified: In `` Sokka 's Master , '' Sokka expresses self-doubt and worry that he is not contributing as much to the group as his bender companions are .