The 'Real You' is not a myth, and it is not based on thoughts. It is what you truly are, and what is lost when you die.
I don't think it was ... if anything "it is not based on thoughts" would imply the opposite!
An object "is" an object whether it knows it is or not.
EDIT I think maybe you're interpreting the final clause of the sentence "what is lost when you die" as "what is lost to you" but I read it as "what is lost to others".