My anxiety doesn't go away from winning though. Reaching a ranked floor helps slightly, but really the only solution for me is to play something I find fun. If I succeed, great! If not, oh well.
You claim to know when a game is lost due to reasons beyond your control, so that is when you should take a break. Even if for just a few minutes. That being said, I find it hard to believe that every one of those losses has nothing to teach you.
I like to watch streamers and these people play more games in a month then I might in a year, so they clearly know a lot more about the game. Despite their vastly superior skill and experience, they still question their own decisions and take time to consider the options. Even something as simple as which cards to mulligan in a matchup they have played hundreds of times by now. Why? Because they are likely taking a lot more into consideration than I would think to.
My point is that there is ALWAYS room for improvement. Yes, some games are 100% beyond your control and will be lost despite making zero mistakes. That doesn't mean there is nothing to take away from these losses.