For one, if you're going to quit the game, I don't think you should beat around the bush about it. If you're causing hurt to yourself by having all of these problems and habits, you really should take a break from the game. Just chill and chat with the community and when you feel better give it another shot. Because I'm sure you only have a problem with the game itself, not the community right..? Honestly it just makes me feel bad to see a good player go to waste. You make these huge posts about peach and how to beat certain characters, you have all of this matchup experience, you spend all this time working towards this goal, you get adamant about your character and how she's placed, but all for what? You give up over a problem you have in game, what you need to do is beat yourself down with a stick until you stop doing it if it means that much to you. I'm being literal about this. The main reason people have habits is because their mind tells them the most logical option is that 'habit'. Usually it's because you actually aren't thinking with your head. Talk to yourself while you play, talk to yourself about what your opponent's doing, as if you're not playing the game at all, and instead you're spectating it, you'll find yourself catching your mistakes extremely quickly, and you're paying attention to the game more.
Anyways, if you really want to quit over your mental block, go for it. In the end, brawl isn't something that you should be basing a career off of, it's something you should be doing for a fun time, which isn't happening when you're stressed. I had a situation just like you did, I didn't feel like playing the game, and I would rather draw and learn other games competitively. However, while I was having an hiatus with brawl, I realized that i love actually talking about the game, and just being social with players. Which brought me (to an extent) to this board and is why I'm so active in it, it's something I enjoy, but I also end up learning about matchups and how to play Peach, and my Peach gets better for it.
Honestly, I don't know where I'm going with this, just have fun dude. I don't personally know you, but I'm assuming you're really good with the guitar and good at art. Keep at it if you like it, drop it if you don't. Enjoy yourself to the fullest, if you have the urge to play peach again, come back to the gaming community. We will surely miss you if you quit y'know. Also, don't think so much about the win in brawl, think more about the experience, enjoying the rush of the game, learning something new, etc. Those are the things you really should be enjoying..
To be perfectly honest though, about the peach videos thing, I don't really watch matches with peach, they ****ing take forever. I'd only watch them IRL if I'm rooting a friend on.