That's less about ADHD than trauma, though the first often begets the other. I'm on the same boat. A trauma focused therapist has helped me.
Forgiving myself, allowing myself to suck at something, to not be perfect, were my starting points. I haven't got to know myself yet, but some of me seems to be shining through the cracks I'm growing on my masks.
The feeling of a wasted life is a recurring one. A whole lot of could have beens. I'm suppose to mourn it and let go instead of lamenting it. I'm not there yet.
I do recommend you find a good therapist. Professional help is a must. Good luck.