You face an unusual apocalypse. One which will put you to sleep forever as soon as you fall asleep. You can either give in to this mysterious condition, or fight it by staying awake for as long as you can.
It took me a bit of time to figure out how to 'survive' to the next day and after without falling asleep forever on the first day. Still, even once you figure out the steps, you get the dark sense that you are only keeping the inevitable at bay for a short time. The writing and conversations with the other characters also help to convey the hopelessness of the situation, and perhaps a certain sense of acceptance and tranquility they might find within. If you find yourself in the position where you are the sole survivor, the situation also takes its toll on you. If you can survive well over ten days, the choices all around you work to show that the inevitable is right around the corner.
I don't think there is a way to win this, and I think that's the point. That said, there is apparently a secret ending for the game, but I don't have the energy to try unlocking it at this point.