Don't focus on winning, focus on improving. Your anxiety seems rooted in your inability to reconcile your expectation of where you think you should be at to where you actually are. The first step is acknowledging that you are a beginner. Once you accept that, you can push your pride to one side and recognise losses for what they are; inevitable. Everybody loses. Good players just lose less.
You want to improve, do this;
1) Watch First Attack on YouTube
Start with this episode then go where you please. It's aimed at Street Fighter players, but SF fundamentals cross over into most fighting games.
https://m.youtube.com/watch?list=PL858F4C6F3C3B9612&v=qyQjqoN0hh4
2) Spend more time in training mode, and make effective use of that time.
Here's a First Attack
One by Perfect Legend
And one by Air on learning Ryu for SF4. Consider his method for learning Ryu as a template for learning any character in any game.
https://m.youtube.com/watch?list=PL13KoUNKKsK0Ef1XT6xATls_AWTEblsZf&v=tcMVI-7cn04
3) Play five matches a day, no more, then go to the title menu>extras> replay mode. Watch back your games, take notes, do it over and over. Suddenly those harsh, incomprehensible losses won't seem so mysterious. If you run up against a move/string/combo that seems unbeatable, take a note of it, replicate it in training mode and figure out your options. You will improve far quicker doing this than grinding matches, because grinding encourages bad habits to form. (I'm not saying don't ever grind, but right now, with how you're feeling, it'll only put you in a bunch of anxiety inducing situations that you are inequipped to solve at the moment).
4) Get a training partner. I'll play you if you're on PS4 in the EU. Regardless, hit the matchup threads.
5) Learn another fundamental truth about video games; you're not good at them. This sounds unfounded, as I don't know you, but it's true. Modern games are easy, they have to be in order to shift units. The more you can complete, the more you'll buy. The skill progression is an illusion. Fighting games strip you of that illusion. All you have is your character and your skill. Your character doesn't get more life the longer you play the game, there aren't power ups or better weapons, just your ability to make the right decisions and execute them. Even Dark Souls, reknowned for its brutal difficulty has a levelling system to make it easier. Once you accept that video games have lied to you about your ability, you'll learn to love the challenge of self improvement that fighting games offer.
6) Go easy on yourself. It's just a game. It's not important. If the apocalypse happened and the world was turned into a Mad Max-esque waste land, your ability to flawlessly perform run cancel combos won't mean shit. Go for a run, grab a beer, get laid. The game will be there when you get back.