Same way I deal with the fact that my life, the reasons I live, and everything I ever have or will know is tiny, insignificant, pointless, and will not matter in the least within a hundred years of my death.

Nothing matters, nothing ever will matter, not objectively. I don't live for any reason at all, at the end of the day.

But, does that matter? Who gives a shit if I am small, insignificant, and have no reason or purpose. Who cares if small children don't go to heaven when they die a horrible death? We can't stop it, we can't prevent it, we can't change it.

It's up to you, honestly. The lies you were told from birth, about how X is bad and Y is good, you decide if you want to keep living them or not. Do you keep caring about the deaths of children as if they mean anything? Do you continue caring about your own life if it means nothing? Do you live only for those around you, because they give your life meaning by caring about you? But why does that matter?

We are all slaves to our emotions, in many ways. We feel bad when we see someone else hurt, and we want to stop that so badly. To end pain, to end suffering, because seeing suffering causes us to suffer. It's something that evolved in us to drive us to work as a group, to care for our young, to not kill each other over scrap food.

But those emotions don't matter either. They are chemical signals in a chemical brain that drive your meaningless thoughts. Why follow them?

I know I have turned your question from "how do you deal with death being permanent" and turned it into "how do you deal with nihilism", but I think it's important, because it honestly is the logical conclusion to Atheism.

We are bundles of cells and water going around by our pre-programmed instincts and our society-imposed beliefs trying to get that next dose of feel-good our brain releases when it gets certain stimuli. Nothing more. We don't matter, not at all. Our lives, our existence, nothing about us matters. The things you see, your life, your everything will fade away and... that's it.

So you do you deal with that?

The easiest answer is delusion. Cling to your morals, cling to what you were taught by society. That's the most acceptable way to go about it. Don't think too hard about nothing mattering, try to put it off for another day.

You could give up. You don't matter, it's all over, it's all pointless. The things that drove you are gone. No point in going on, time to jump off a building. People will tell you not to, but they are part of society and they want you around to keep society large and expanding. You will be scared, you won't want to die, but those are just fear responses, evolved to stop you from jumping. Just more meaningless mechanisms on top of a meaningless life. That's a way to cope with it, a very grim and very bad way, but the option is there.

You could find the world a playground! Morality is gone! I can kill! I can rob! I can steal! No guilt! If you think this than I am glad you are outed. I prefer we know if the only reason you didn't hurt people was because of some arbitrary belief rather than the innate workings of your mind. You lack empathy, have your fun while it lasts, society will hunt you down and stop you eventually, and it isn't going to end well in the long run.

I personally believe that it doesn't matter that we don't matter. It's a philosophical question that we honestly should never have been worried about the answer to. Life doesn't have to matter, and regardless of if it does or not, I am going to still head out and smile when I take a bite of a mcdonalds hamburger. I am still going to take pride in building something and showing it to my friends and family. I am still going to remember that, despite anything else, living another day is better than dying. I am a creature who follows what makes me feel good. Does it matter? Not at all. But I don't care, because I am going to enjoy my next day, be it filled with frustration and anger or joy and pleasure. Why not?

Things matter because I assign value to them. Things matter because I stand up and say they matter, and so long as I point at something and I keep stating it, that thing matters. So long as I care, a thing is cared for. All value of all things in the universe, when you are looking at the universe through my eyes, is assigned by me.

I have recently been encountering a situation that I never really had to deal with, that being the near-death of my grandparents. I heard a month or two ago that they were both dying, mental issues, breaking bones very often, moved into a home, repeating conversations, the whole suite of "old people problems".

And I feel horrible when I think about it, and I tried to sit and wonder why. I came up with the simple reason that I am morning loss, rather than death. Thinking about going to a dead persons home and seeing where they used to be, but instead they are gone, is worse than the fact someone is dead. To me at least. Why is that?

I do not feel bad when a person dies, I feel bad when I lose a grandparent. When the person I could go to at anytime, a person who I could care about, a person who is the whole reason I exist, is gone. I do not feel nearly as much when someone who is just as much a person dies as well.

I do not feel bad at the loss of a child. I feel bad for the loss of a person. Someone who could have grown to have a life, to have children, to make others happy, to grow, to become something greater. The child is meaningless, that isn't what we mourn, even though society puts so much focus on that loss itself. We morn the injury to the parents, the loss the family feels, the pain those around us go through. We morn it because it hurts us as well, to see them hurt.

Why does there need to be some sort of cosmic justice? Why do we need some sort of great power redeeming the death of children? Would we not still cry for our loss even if there was a heaven? Do Christians not cry for the losses of loved ones, even the greatest believers. They aren't dead! Not to them! So why be sad at all?

So how do you deal with it? You learn about it, and you think about it, you make your own little rants like I have above. I can't tell you how to deal with it, but I can give you my opinion and hope it helps you a bit.