If we exist as past, present, future states of self only as perceived in linear progressions of time as non-existence, existence, death. What if time is not linear and we are in this moment both existing and non-existing and will always be, have always been in this state? What if change in condition of life or death is viewing one fragment or another of the constant whole? What if it's casting a shadow from different sides of the same constant?
That state that you are describing, kind of one outside of "time", is what I understand as the divinity and God, perhaps the "church ascendant", ie angels and saints too but I am not even sure about that myself.
I am a Christian/RC believer but in the main I believe in the idea of the Buddhist or Hindu "pure land" religions which have the majority of people experiencing a kind of "quantum immortality" and reincarnation perpetually, only I would call this state "purgatory". Its got to do with "sin" but not as most of its secular critics understand it but as Eckhart or the mystics did which has real parallels with buddhist ideas about attachment to worldliness.
The fear of death I dont think is entirely about fear of pain, fear of disembodiment, dissolution, nothingness, as all those things, in theory, are experienced during sleep, drunkenness, narcotic or anesthetic sedation, those "little deaths" or if you consider philosophically, the thousands of years of your "pre-birth existence" (to reference Schopenhauer).
I think it is to do with not being "satiated" with life, not having had enough of it, this is a kind of radical life affirming understanding of worldliness, since I do think that creation was/is a gift from God. The final judgements posited in allegory or story from the Jewish traditions in which recording angels or God asks the newly perished soul why they didnt bother with all the joys, rewards, good things in life make sense. I've read about near death experiences in which people approach death and someone or something asks them "what about..." someone or something of a worldly character and "zip" they're back like they just hit up "continue" on the "game over" screen.