I share your pain as well.
I never really cared about winning in the first place, but I would get frustrated every now and then when moves don't come out or I just black out against someone I know I can at least put up a good fight with. It happens to the best of us. I sometimes get discouraged because I do black out at times, and keep in mind its with characters I do know how to use. Then when that happens, I get frustrated. Then I lose more. Then I get even more frustrated. It's a vicious cycle when that happens.
I agree with InWiththeAshes. You have to remain positive, no matter what happens. Now, I tell myself that I can do it. One day I'll reach my goal but it will take time. You need that type of mentality. Right now, I'm playing Persona with probably one of the hardest characters to win matches with if you don't know what you're doing. I lose matches every now and then but this hasn't stopped me from using her, watching videos, hitting up training mode, and dealing with her hard matchups.
It's hard, and you may feel as if you can't compete with better players. I have been there, but I am slowly getting out of that mindset.
YOU CAN DO IT.
I'm not sure if you're on XBL or PSN but I can help you out with Lambda/be a sparring partner. I don't play as much but I still remember how to use Lambda.
Waaaaat? I liked your Yukiko.
Don't go to the darkside with Yu damnit.