As for me, i wish i had the state of mind that i have now- while i was a teen, so i didn't have to go thru years of body dysmorphia and self consciousness that took a huge toll on me mentally and psychologically.. id tell my younger self that i was fine the way i was.
i definitely have more (now) to be self conscious about, like my slightly crooked thighs and knees due to arthritis caused by my autoimmune issue but i don't let it bother me. i just don't care what people think anymore.