Respectfully, you don’t need to quit your job. You need to go to therapy. Your manager and supervisor both affirm that you’re doing well. Your inability to accept their words as truth has nothing to do with your ability to do your job and everything to do with the state of your mental health. Quitting will do nothing other than lead to chaos in your life, further wrecking your self-confidence. What’s the point? And quite frankly, even if you are genuinely not good at your job, the solution is not to quit. It’s to learn how to be better. That’s what being an adult is. Don’t know how to do something? Cool. Learn how to do it. Then you know. Accept that you need some help for mental health issues and then get that help. Don’t blow up your life for no reason. There’s literally no point.