The reason was, instead of trying to play and learn and get better, I was just trying to play better. It sounds like not a difference. It sounds like "Well, of course you try to play better! What's wrong with that?"
The difference is, you have to get better to play better. You can just go from platinum to masters or even diamond in a single game. I can't just decide "Ok, this game, I'm gonna be perfect at macro and perfect at micro and multitasking and I'm gonna demolish everything put in front of me." You have to work to get there. You have to practice, you have to learn the game, you have to train your responses and your multitasking.
Expecting to just be able to, in a single game, go "Ok, now I'm pro-level," is not just unrealistic, it's setting yourself up to fail, and worse, to rage. You're not gonna do it, but because you're expecting to, and you're falling so short, it puts your skills and self-worth into question. "I was supposed to be awesome that game? What the hell happened? Am I just a scrub??"
So, I stopped obssessing and expecting. I play stupid games with friends. I played some Desert Strike with buddies, played some FFA with lower-league friends, played some 1v1s to try to help them with their builds. Showed them some cool custom maps, like Darglein's Micro Trainer, Darglein's Multitasking Trainer, Multitasking Trainer, Build Order Test Zone, etc.
Also, I've been finding and picking out streams and replays from pros and high masters/gm players I like and going through them and trying to note a lot of stuff like builds, timings, responses and stuff. But I did that before. However, the lack of the usual frustration and intense search for direct answers, I feel like I'm learning more from them.
I've been laddering, but I also changed my ladder methods. Rather than just trying to slam through a set number of games, and obsessing over my performance and the reasons for my wins and losses and analyzing replays as I go...I'm just laddering when I feel 'warm' and just giving a few games my best shot until I don't feel like going anymore.
Oddly, this seems to actually increase the number and frequency of my ladder games, and lessens the amount of games I play 'on tilt'.
Then, rather than obessing with performance as I go and analyzing replays right after that game, I wait until the morning after to look at the replays. I find I'm a lot more able to be objective that way, and when I see a mistake I made, it's easier for me to just note it and think of ways to fix my mistake(s), rather than just raging at myself for being bad and playing the next game even worse.
All this seems to be combining in a way that I feel like I'm actually improving and increasing my skills and maybe I'll even make diamond sometime! That would be awesome.