There’s a framework here that I think it’s important to be conscious of.
You’re saying you’re a nobody relative to the vastness of the universe, and that recognizing that is the purpose of life, and is more important or more true than the fact that you’re a somebody relative to the space and time scales of a human life. But that perspective is also true and important.
You’re also the entire world to countless generations of microbes that call your body home.
I think the key is to recognize the appropriate scale and context for each of your actions, desires, or anxieties. Whether I step on an ant doesn’t matter to the universe much at all, but it matters a bit to the little kid watching me, and it matters a whole lot to the ant itself. And whether I’m comfortable with my insignificance on a universal level might matter a great deal to me, but not at all to the person next to me on the bus.
It’s all true, and it’s all important. The purpose of life is maybe more to understand those scales and live in harmony at each of them.