In the State of Qi there was a man, who feared that the sky would fall down, and there would be no space for his body. He could neither sleep nor eat.
Not too complicated, is it?
There are a few slightly different versions of the story. In a more extended one, his friend walks up to him and tells him to calm down. The man answers: “But if the sky won’t fall down, the stars or the moon or the sun may!” His friend walked away in frustration.