So lets start out by stating that I'm an ex lay preacher who became atheist a couple of decades ago. Even when religious I had the same concern so here goes:
As I always understood Christian heaven, in a nutshel,l to be an eternal paradise of unending bliss
You may want to disagree with that argument but what I write here is based on that assumption. Ignore whether you think heaven exists as my point is that heaven, as described, scares me
Eternity is a long time. Longer than any of us can imagine.
I don't know about you all but I eventually get bored. I cannot think of anything that would occupy me for eternity. I can't think of anything I recognize now, or anybody that would not irritate me after some period of time.
Now, permanent happiness means I cannot get bored, or irritated, or even a bit miffed.
Happiness/bliss is another interesting concept. As humans we can argue that happiness is any time we're not miserable. This somewhat trite statement is my way of saying that you need something to contrast with to understand when you are happy. At the very least you would need memories of past unhappiness - which in themselves could make you unhappy in order to understand them
What I am clumsily trying to say is you cannot truly know you are happy without having some unhappiness so being in a bliss-only state makes no sense.... how would you know?
My two threads here (happiness requires unhappiness as contrast + boredom is unhappiness so I can't get bored for eternity) seems to me to make heaven an impossible concept.
There is one exception - what I like to call the 'stoner' heaven. In this just an essence of you continues forever. Your unrealized ambitions, desires, hates, needs, memories, relationships are all missing. It's like you are so stoned everything is just... cool man....
In this case the eternal bliss heaven would be possible and I can cease worrying about being bored, but to be frank, heaven doesnt really contain me, it contains a fraction of me that spiritually gives a grin with glazed eyes and comprehends nothing.... a sort of persistent vegitative state.... you are 1% of what you were.
So, in trying to square the circle of what heaven means as a concept I either face trillions of years trying to occupy myself, or I face a spiritual coma
Neither option seems worth the effort and both seem more of a punishment.
Does it scare you? How do you visualize spending billions of years? How do you expect to be able to maintain permanent happiness?
This is not a religion bash - it always nagged at me both when religious and when not.
BTW people ask what an atheist death is like.... well when you are dead, for you, it is like it was before you were born. nada.