I do try to make a positive impact, but in the "leave things better than when you first encountered it" sense - I see no reason to worry about, or even be concerned with, "greater" things like "a better world", "a mass extinction event", or "humanity".

My "sphere of influence", and therefore my interest, is limited to the people and things I come across.

I may not be able to (nor care about) solve world hunger, but I can make sure my sister doesn't have to eat ramen and work three part-time jobs. I may not be able to solve the world's unending conflicts, but I can lend an ear to a friend who's undergoing some rough patch. I may not be able to solve climate change, but I can pick up the trash on the floor.

And, frankly, that's enough for me.