Once upon a time in the state of Qi, there was a timid and somewhat neurotic person who often thought of strange and inexplicable questions.
One day, after dinner, he took a large fan and sat in front of the door to cool off. He muttered to himself, “If one day the sky falls, what should we do? We have no way to escape and will be crushed to death. Isn't that too unfair?” From then on, he worried and troubled about this problem almost every day. His friends saw him in a daze all day long, with a haggard face, and were very worried about him. However, when everyone knew the reason, they all came to persuade him, saying, "My dear brother! Why bother yourself about this matter? How could the sky fall? Even if it really falls, it's not like that. You can solve all your worries and concerns alone, just be open-minded!" However, no matter what they said, the man still didn't believe it and often worried about this unnecessary problem.
Later people created the idiom “like the man of Qi who was haunted by the fear that the sky might fall -- to entertain imaginary or groundless fears” based on the above story. Its main meaning is to awaken people not to worry about unrealistic things, which is roughly the same as the meaning of “worry about troubles of one's own imagining”.
从前在杞国，有一个胆子很小，而且有点神经质的人，他常会想到一些奇怪的问题，而且让人觉得莫名其妙。
有一天，他吃过晚饭以后，拿了一把大蒲扇，坐在门前乘凉，并且自言自语的说： “假如有一天，天塌了下来，那该怎么办呢？我们岂不是无路可逃，而将活活地被压死，这不就太冤枉了吗？” 从此以后，他几乎每天为这个问题发愁、烦恼，朋友见他终日精神恍惚，脸色憔悴，都很替他担心，但是，当大家知道原因后，都跑来劝他说： “老兄啊！你何必为这件事自寻烦恼呢？天空怎么会塌下来呢？在说即使真的塌下来，那也不是你一个人忧虑发愁就可以解决的啊，想开点吧！” 可是，无论人家怎么说，他都不相信，仍然时常为这个不必要的问题担忧。
后来的人就根据上面这个故事，引伸成“杞人忧天”这句成语，它的主要意义就是唤醒人们不要为一些不切实际的事情而忧愁，它与“庸人自扰”的意义大致相同。
