Switching between characters and fighting games melts my brain. How do you guys remember this much?
Like others have said, only focus on a couple of characters per game. Also try to play characters that fit your overall play-style or needs.
For me, I like trying to learn a rushdown character, a zoning/keep-away character, and MAYBE a trap/set-up character. I only try to focus on 2-3 characters at a time.
I try to learn all characters to an extent so I can try them all of course, but to also get some knowledge on how to counter them since I'm also learning their weaknesses. But again, I only "main" 2-3 characters. 1 main, 1-2 pockets.
Also only try to focus on a couple of games. Right now I'm pretty much only playing Mortal Kombat X. I've pretty much dropped SFV at this point, and I only turn KI on sometimes now. I don't know what games you are playing, but if you are playing (let's just say hypothetically): MKX, SFV, KI, KoFXIV, GGXRD, and so on, then don't be surprised when you are getting beat by people in MKX that exclusively play that game only.