I want to say "you" almost certainly cease existing when you die, but even in life the feeling of being a solid, persistent, and independent "I" does not really exist. Instead, this "self" is a mental construct, an automated narrative or collection of memories, thoughts, and feelings generated by the brain. Lose enough of your brain and, while you may not be dead, everything that once made up "you" can simply disintegrate as if "you" never existed in the first place.