Eternity
As someone who already loves movies about second chances or reincarnation I liked this one even though the script was a bit different.
If you ask me the absence of heaven or hell is more terrifying than their existence because when you think about it everything you've believed in and been committed to your whole life seems meaningless. Of course you'd say that eternity shouldn't be like this.
That's why having someone you love by your side fills the void but the fact that you only have one chance to decide makes you anxious.
Particular scenes made me cry when I was watching this. But you know the ending was satisfying so in my opinion it was worth crying over.