Have you ever had one of those lives? You know, the sort that last a few decades and which tend to be defined by their mistakes? It's a real downer when you think about it, we waste so much time (all of it, really) on things that are not only meaningless but ephemeral; the things which we create with our minds, hands, and loins, we're lucky if they last more than a century beyond our own death. Even then, they too are meaningless. It's rather sick, really, to have existence without meaning and still wish beyond anything else to continue it, existing purely for the sake of existing.
You can take solace in the traditional solution to the Sisyphean problem and impose your own meaning on meaningless life, but that created meaning only lasts as long as your own existence; once you cease, your life retroactively ceases to mean anything, except in distorted second-hand reflections captured by the individual meaning of others, which will also fade with death until not even a perverted fragment of your own existence persists.
You try to take joy in the immaterial, in your love and affection for others, until you realize that there is no true understanding outside of fiction, that it is utterly impossible for two human minds to comprehend the totality of each others' existence. Worse still, most relationships do not even pretend to that, remaining little more than the conversational equivalent of apes picking insects from their comrades' backs. Even among the very closest of relationships the closest two people can come to understanding is the possession of a vast body of shared experience, which itself is at best a shallow understanding, comprehension of the shadows cast by the light of the other's soul shining around the metaphysical forms of those experiences, seeking to understand the nature of the thing by how it is affected by circumstances, your own understanding of which is distorted by your experience.
It is truly terrifying to realize that not only will you cease to exist within a cosmic eyeblink, but that nothing you do, even when impacting the existence of others, contributes towards that joining of minds, true understanding of another being, continuity by proxy--a shallow shade of life, but even that is denied us. Even those you care most deeply for are still at the core utterly alien to real understanding, only explainable through metaphor and rough generalization. Life without meaning or purpose is no gift, and yet it is worse still to consider losing it, even when comforted by religious lies and false bravado, platitudes about dreams which must end, the hope of the desperate that existence is not finite. It is at the root of our minds, the one true shared point, the heart of all civilization and culture, even the drive behind our most basic biological instincts seeks to prevent the cessation of existence. And yet it is futile, doomed to repeat the process ceaselessly until all existence comes to an end. Seven billion voices fill the sky, each searching for comfort and company, each desperately alone, each doomed to fade away unremembered.
I fucking hate myself sometimes. Or possibly just the part of myself that won't let this go, that brings it up every damned night when I'm trying to sleep.