The base of that goes back to a very simple realization: On a cosmic scale nothing that we do is of great importance. This planet likely is not as special as we would like to think it is and we are not as special as we like to think we are. We are to the universe as a single bacterium is to us.
https://www.youtube.com/watch?v=0fKBhvDjuy0
Is a nice recap of just how vast the universe really is and how utterly insignificant we are within it, in spite of all we're figured out and have achieved collectively. It certainly humbles me.