Quitting Adderall is like learning to a adjust to being a different person, with different shortcomings, interests, and abilities. It takes time, especially when you are flooded with memories of who you "used to be." Most of it is in your head - which is not to say that it isn't real - just that it's not biological.
I would recommend reading the book the "Feeling Good Handbook" to help you correct some of your thinking patterns in a way that will help you ultimately be more positive, productive, and accepting of who you are. It is easy infer that after quitting adderall it is inevitable to feel lousy, tired, unproductive, and mentally slow. I don't believe this is biologically inevitable. The way you think sharply impacts how you lead your life, and you can change how you think -- at the end of the day, it is the only thing you truly do have control over.