Question: How can I get my 14-year-old to not be so critical?

Coach, when my 14-year-old son comes home from practice and the only one criticizing him is himself, it is frustrating. As a goalie, he is pretty vocal on the field, except for when he makes mistakes. The angrier he gets at himself, the worse he plays. Is there a technique to somehow curb that anger and frustration so it doesn't mess him up, or does that start to become a maturity thing?