Our 10 year-old son is very keen on competitive sport. He's active since he was very young and he's always really enjoyed it. The problem is that recently we've noticed a change in the way that he behaves when he loses. Either he becomes very angry, resenting his opponent and sometimes us if we're not sympathetic to him, or he becomes distant and quiet often for a day or so after the event. I want him to enjoy sport and be competitive but should I be worried about this?