What is the self?

I didn’t want to derail a recent thread about delusion, but I think it might be worth defining what we mean when we refer to the self (or “I”).

Are we our brain? Our consciousness? Our entire body?

If you feel that “you” are your entire body – if you were to lose one part of your body at a time to a progressive disease, at which point would you stop being “you”? And if you feel that “you” are your brain (or “mind”/consciousness) – what level of damage/disease would be allowed before you are not “you”?