present new opportunities! hockey is a game of mistakes, and you have to have a short-term memory.
in the situation you describe, where your son missed a clear shoot on goal that would have won the game, i think you need to start by swallowing your own feelings, and ask your son how he’s doing. in the rare instance, he may surprise you: "dad, i did everything i could to make that shot, but my aim was just a bit too wide."
in the more likely scenario, he may not be ready to talk about it right away. don’t push it. you can ask how he’s doing and then let him come 