World War III started with competition for resources and ended with resource scarcity.
The people left behind after the war cling to the shadows of the past and live happily, guiltily or remorsefully.
What supports them to survive may not be a strong desire to survive, or a strong bond, or it may just be a broken shadow of memories of the past.
Living on your last breath is still alive, being happy is still alive, living with self-blame is still alive - as long as you are alive, everything is still possible...