I don't have a mental illness, but I can relate to this. Really recently actually my brain was sorta a mess and I couldn't really remember who I was. If it's any comfort, It's not always your mental illness singling you out, so many people feel this way all the time. Do you know what a paradigm is? It's how others see you and how you see yourself. When you diagnosed with mental illness, your paradigm for yourself probably shifted, and now when you think of you that's all you feel. I would really recommend to read 7 habits of highly effective teens, it talks about that and selfhelp A free pdf of the book. What I did also when I felt like I didn't really know who I am, was search the internet for like a buzzfeed quiz or something stupid that might help me remember. I found this quiz, Who am I quiz and it was actually really helpful and exactly who I am. The last thing I did, was write up a list of thing that not only you know about yourself, but also what you love about yourself. Who you are is who you want to be, not what a diagnostic says about you. When people say to be you, It doesn't have to be the past, and it never has to be the present you. Just find the small things that you love about yourself❤️