A daughter tells her dad that he's going to be a grandfather. He cries, overwhelmed by emotion. This, my friends, this is is what life on Earth is all about: We're here for an infinitesimal fraction of cosmic time, your DNA is the only thing that will stay behind.
At least, it will be the only part of you that will remain meaningful when you start your journey back to the stars, transformed into elementary atoms.
At the planetary scale, life on Earth revolves around endless reproduction, which is what makes evolution possible. At the human level, scientists say, this is also what ultimately gives us comfort when we think about death and our place in the world. It may just be an illusion conditioned by those millions of years of evolution but, as far as we know, the feeling as real as it gets.
And that, believe it or not, is the reason why, deep down, this man is crying (and me too, I've to admit.)