When I was younger, I read a young adult book called Elsewhere which followed a 15-year old girl who died, went to heaven, but in heaven (called Elsewhere) you age backwards until you are a newborn and then you are sent back to Earth to be reincarnated. When I was like 13 reading that book, it gave me this fear of dying and then not being able to reconnect with my friends/family afterwards (not spoiling the book by saying this, but that is a big thing the protagonist grapples with)