The three Western religions--Christian, Jew, Muslim--have their individual ideas about the afterlife. And what you do in this life will determine how you spend that eternity. But, what's the reality of such things?
Most people realize that the heaven/hell concepts are bizarre at best and superstition at worst. But they still want to go to heaven. It's a matter of being narcissistic enough to think one should live forever in joy, luxury, and in the palace of some king. Silly, eh? Plus, they forget that all kings are basically jealous dictators. All one needs to do is read the Bible to see just how jealous that particular dictator is.
But we just cannot seem to accept that maybe, just maybe, there is neither a heaven nor a hell awaiting anyone or anything, that no devils and no angels are preparing for our arrival when we die. Still, we cling to our hope that we are eternal.
Are we in fact eternal? Probably. But not in a religious sense. We are energy, made from the energy that has existed in the universe since its beginning. We have come directly from the stars, those little twinkling lights 'up there' that seem so far away. But in reality, we are living in the midst of them, our parents, our creators. And we are never separate from them...or each other.
Death is just change. Again. And in all likelihood, we will simply dissolve back into the energy from which we sprang. That is a very good thing. Besides, where else would we go?
As long as the universe exists, we are indeed eternal.