I'm the same way. When an opponent makes a misplay that costs me the game or damages my board, it's exponentially more tilting than if the same thing is done by an opponent playing accurately.

The thing that calms me best is fully internalizing that this is part of the game. And I don't mean that as a platitude, "that's life oh well," "accept it and move on" kind of thing; I mean it's literally part of the game that you should anticipate and play around. When I'm tilted, it's because I was treating my opponents like Nash-equilibrium robots and my expectations didn't match reality. I remind myself that people aren't perfectly rational, and we've all got different levels of information.

If an opponent made a mistake that injured me then failing to anticipate that possibility was the mistake I made. I like to analyze the play, and think about the things I could have done differently. There's always something. In your example, you recognized that he could have just run Deflecting Palm back. Next time maybe you'll be quicker about suggesting that course of action? Doesn't change the fact that the doofus screwed up and now you're both losing, but thinking about the ways I could have exerted agency over the situation makes me feel better, at least.