I think that emphasizing the listeners point of view is the way to go. Ask them kindly how they would feel if another child approached them and said matter of fact-ly that they were a terrific skater or a super reader or will be the next Picasso? Help him walk through the feelings that might arise on the other persons part like jealousy or annoyance or boredom.
Of course, it is totally normal and will pass but I think a good way to get through it is to work on empathetic speaking/listening.