Congratulations. You drew the intelligence card. You're right. This is all like one big board game where everything eventually goes back into the box. Your money, possessions, accomplishments, productions, ideas, thoughts, and feelings. Back to the box. So pick a character class compatible with what you rolled and don't forget to have fun.

Oh, and head up; you're going to suffer anyway, so make sure to maximize how much of it is by your own choosing.

I give it value.

Value is just some human made up currency after all. "Is it worth the time?" etc.

If I were to approach life with the mindset "well everyone I know is going to die some day and humanity will die out so what's the point?" I'm not going to have a very positive outlook to life.

But I figure I'm here. I get 90 years or so if I am lucky. I might as well enjoy them while this combination of atoms is me.

Doing nothing does that for me. Seriously. I'm regularly confronted with this feeling, and one thing I found over the years to consistently lift me out of that trough of meaninglessness is meditation. It boils down to "if nothing seems to matter, then just don't do anything". But I have to resist the temptation to just engage in some form of escapism and just sit there with that boredom. Initially it's hard, but after about half an hour to an hour the feeling of boredom and meaninglessness recedes, and my mind becomes more calm, focused and purposeful. It's as simple as that, at least for me.

There are multiple ways to look at this.

One is to stay small - the things you do matter in your individual sphere.You don't take care of your body, you die. You don't exercise your brain, it atrophies. You can increase this sphere to friends, families, community etc till you can see the effects and have feedback. Of course as in all system, those might be a bit delayed, so it helps to have some context.

Or you can go meta, why should things matter. This innate drive that we have to find meaning in all things is very confusing. Things simply are - accept them.

And if nothing actually matters at all - then you have a blank canvas to paint what you want.

I've began to see nihilism as a memetic virus or disease. Once you begin wandering outside the boundaries where you were raised, you almost invariably end up catching the nihils. Some people have few symptoms and can easily continue living meaningful lives. However, other people are heavily affected by them, and become abated and purposeless. We know the symptoms to the nihils.

Then, it's a matter of taking care of yourself and antibodies will begin to build.

I know you are asking about this second part, and I'm sorry I can't give you a straightforward answer (a vaccine, could be said).

The most I can be confident to say is that, as every memetic phenomena, it has a strong subjetive charge. I don't think it is 100% subjective, as humans have more in common that we'd like to admit. And, most likely, the best vaccines for your case are already suggested and proven countless times before. Don't try to reinvent the wheel. Also, be wary of bullshitty alternatives to vaccines/medicine (superfluous and toxic feel-good coaching).

If nothing matters then there’s no reason not to.

Maybe by understanding that “mattering” is a subjective, internal thing, not an objective property in the world.

Can I ask where you're coming from with this question? (just want to understand the context before I answer)

To understand that worthlessness is worthless leads to the Buddha.

-- from Why Has Bodhi-Dharma Left For The East (1989)

Therapy and lots of it.