Knowing humans won't live forever, why don't we just live normally?

I just see it as, what's the point in trying? I keep seeing sooo many things online, "in a million years humans won't exist", "in 500 billion years the sun will destroy Earth" So then let's live with treating everyone around us with respect and kindness and just live our lives in the best way that we can. Like why bother figuring out building a colony on Mars. If humans are gonna be extinct in a million years, what's the point? Then I saw something about an asteroid possibly hitting Earth as late as 2035, depending on which way it goes? So it might not even be a million years. I thought NASA did that big experiment with blasting an asteroid in space? So if an asteroid is heading for Earth, which we know *could* be a possibility, if that time comes, I think NASA should try to hit it and at least try to break it up into smaller pieces at least. Oh right, they just need money. I'm like, DUDE!?! AN. ASTEROID. IS. HEADING. FOR. EARTH. WHAT. GOOD. IS. MONEY. IF. IT. ACTUALLY. HITS. US??!! Like no one gets that argument and it makes no sense, and it's the most sensical argument I can think of.