He's still pretty bad at handling losing though, I think it's because he tries to put a lot of effort into thinking about a strategy so when it doesn't come off it's like a lot of energy has been wasted. I generally don't like to put too much thought into things because I want to relax when I play games and I hate games that feel like work!
I'm super competitive in games like your friend. I enjoy putting a lot of thought and energy into my turns. I love it when a complex strategy comes together and I win. But you know what's even more fun than winning? Losing.
If you win there's nothing to learn from the game. However, if you lose, you were clearly outplayed and outsmarted. Your strategy came up short. Now you're able to analyze the game, figure out your mistakes, and do better next time. Losing is awesome. If you're competitive than you want to be good and you want to keep getting better. The only way to improve is to lose to a better player. Competitive people should want to play against people who will beat them.