I have figured it out with CS2. I was focusing on the outcome, when I should have been focusing on my execution. You see, I can die in a duel, that is fine. I'm not gonna win every single duel. But if I know that I executed it to my abilities then I still win that duel by default. This has been making premier far easier to play and far less stressful. Before, I was positioning myself as an experienced player who has cracked aim in warmup, therefore I should win more or less 70-80% of matches. And when I lose duel that I "thought I should've won" then I got frustrated. But the thing is is that frustration actually just made me play a whole lot worse. It made me panic whenever an enemy appeared, it made me become toxic towards teammates, it was just not good in any way. I also cared far too much about my rank and, although I still care about it, I don't feel as if I deserve to be in a high rank. I was placed at 17k when I started, dropped down to 13k, and now I'm almost at 15k just from this new way of playing. And forget the stats, I wanted to drop 30 kills a match. But that's just not feasible. I haven't actually been playing for 10 years straight, it's more like 10 years on and off with big big gaps in-between. So I shouldn't really expect to be the top rank.
So, this is my new way of playing. It's to forget whatever you "think" should happen and focus on what actually happens. And if I execute a duel properly, stop moving properly, control recoil properly, make sure I actually land my first bullet, then I performed well. Even if I lose the duel, it doesn't entirely matter that I lost. It matters that I didn't fold under pressure which is infinitely more rewarding and valuable in terms of longevity if I'm going to play this game more and more again. I remember back in the day I would seriously get angry. Like 2015 it was absolutely chaos.
Update, I just had a very depressive episode but after Kira suggested I tidy my bedroom then I became alot better mood!