Is it normal all adults are miserable

I am miserable and I have anxiety and some depression. Ive never met a single adult actually who did not. Even those whose seemed free spirited, positive and happy has had depression or something. They just had learned healthy ways to manage. I have no motivation or any of the creativity I had as a teenager. One always thinks theyre not going to turn into a boring, bitter adult without imagination but then it happens.
I am very disappointed.