So this is the whole world, yes? Nothing left behind and nothing to leave behind?
So what choice do you have? The last thing will be your state of mind. What do you want it to be? What control do you have over it?
Without getting too flippant or too philosophical (though feel free to do both) there's a Lars von Trier movie that confronts the existential question. Trier (a self-confessed depressive) has an end-of-the-world story where a group of people face the inevitable together. One person (played by Kirsten Dunst) leaves the group to face it differently, alone, embracing the inevitable.
Depending whether you find her ending beautiful and uplifting or not, the movie is beautiful, uplifting or not.
Hidden Image/Members Only(This is not the image from her final scene)