Demonstrating the existence of something is as difficult as demonstrating its non-existence. I don't know whether heaven exists, but I find that idea equally harmful as false hypotheses about the world. Just like previous civilizations that couldn't explain natural phenomena created gods to provide explanations about the world. If you accept that idea as truth, you will form more hypotheses based on that premise. What is the hair color of the god of weather? As ridiculous as it sounds, that is the danger of accepting non-verifiable facts as truths. The notion of reality succumbs to the conjectures of your mind.
Don't get me wrong. I miss loved ones who are no longer in this world. The idea of another moment where I have the opportunity to appreciate their existence forces me to think of the possibility of life after death, or at least a form of consciousness that perceives the physical laws of that dimension. However, it's a mechanism of our brains to comfort us from this painful experience, even if the idea completely goes against our rationality.
A common conjecture I find when thinking about this is the hierarchical consciousness of the death dimension. That was the fancy term I created to simply think of the separation of minds that have been dead for more time than others, giving them more experience than the recent deaths. Let me do my best with this example: Abraham Lincoln died 160 years ago. If I die tomorrow and I get the chance to "talk to him" in that dimension, he already has 160 years of experience in the afterlife, so he can show me "how things work around here." The same with the random caveman that died centuries ago trying to hunt an animal four times bigger than him. He has more experience being dead than every single one of us in the Z generation!
Assuming eternity or even consciousness after we die is a very optimistic expectation of this mystery. Or maybe people who don't quite understand the first law of thermodynamics would argue, "Energy in a closed system can't be created or destroyed, so what happens with our energy when we die?" Aside from scientific misunderstandings, this whole idea to confront the loss of our loved ones causes even more incongruences and false hope during grief. I even find it disrespectful reducing the memory of another human as if they were looking at us from the sky to make sure we are doing right. Do you really think my grandma will be doing that rather than enjoying the conditions of that dimension? Come on, a weak argument that only a weak mind would buy. The same people who bought indulgences before the Protestant Reformation.
The existence of a human can only be interpreted by another human. This is another symptom of trying to impose human attributes on the universe. That's why progress in science required an incredible imaginative effort to bring accurate explanations about reality (or a portion of it). But just because we can't see the entire electromagnetic spectrum, it doesn't mean that it doesn't exist! It's because we are conditioned by our human minds to perceive reality through our biological limitations. If that's the case, the same sociological structures will form in the afterlife because we need to coordinate how we'll find our loved ones when we die. Again, assuming our loved ones still "exist" in another dimension, that's a problem that may arise if that is true.
Immortality can only be achieved if you make it into the history books and someone centuries later calls your memory by reading the texts, just as we do when reading passed-away authors. I prefer to confront the truth that my loved ones are no longer here, and I can only honor them by recalling the moments we lived together. Perhaps this way, people will truly realize the precious gift they have in their hands: the time to experience this life among the people you love, contributing to humanity because there's no second chance. Every moment is unique.