It's important to differentiate between things that matter to my emotional well being and things that matter in a universal sense. Plenty of things matter to my personal monkeybrain - I want to have a stockpile of nutritious, calorie dense foods. I want to feel free of danger from predators and natural hazards, I want members of my tribe to prosper and multiply, etc. All those things might as well be noise on the universal scale.
It doesn't refute anything. The point is rather; what matters to you is part of your personal journey. Ultimately it still doesn't matter in the grander scheme, but that isn't the point of enjoying your adventure while you're around.
Does the cosmos care if I give my Mother a birthday present or not? Unlikely it does. Do I? Yes, I send one every year. Does it matter then? Not really, but I like doing it because I like being nice to my Mother.
I think we nearly agree, but I’d say you’re throwing the baby out with the bathwater.
The bathwater is the notion of a subjective cosmos, some overarching supreme being to whom specific events ought to matter somehow. I’m very happy to throw out that bathwater, along with other theocratic sophistries that still influence our thinking too much. The baby is meaning itself, all of which takes place within the cosmos, and every instance of which is subjectively experienced by some specific subject, by definition. And crucially, these subject–object connections can themselves be observed by third parties as real, objective phenomena through abundant evidence. They are as real as potatoes or sound waves.
This part of your comment feels like a non sequitur:
> Does it matter then? Not really
You just said it matters to you. Then you said it doesn’t ‘really’ matter because it doesn’t matter to…the cosmos as a whole? So what? It doesn’t matter to your toaster either, nor to my cat, but it still matters to you. For something to ‘matter’ there must be some particular object that matters to some particular subject, and in this case the subject is you. Your reason for doing it doesn’t mean it doesn’t matter to you, it’s just an explanation of why it matters to you.
And to me, sure, those things matter. But I also acknowledge that this isn't an objective thing the cosmos put into the world but a personal feeling. My argument is essentially that you've got to do that. Acknowledge that what matters to you is something personal. And to cherish that because the journey is important. I see it as a pathway to positive nihilism.
Yes. By induction, if nothing matters, then they don't matter either.
It helps you relax and put things in perspective. For example, you can focus on achieving high scores just for the sake of it. Have the kids you want, have the life you want, have the things you want, knowing that it's pointless but that you want it and that's enough.