When my daughter was younger, I practice rephrasing that with her. All "I can't"s were replaced with "I'm having a hard time..." or something similar. She's 15 now and "I can't" still is not just accepted as a solution.
It sounds like he might not be feeling all that confident. Maybe to balance the things that he feels like he is having difficulty with or not excelling at, throw something in there that he will enjoy and do well at without the angst. Swimming lessons? An art or dance class?