【成语来源】 

Fear is often greater than the danger. 
杞人忧天

In the Spring and Autumn Period (春秋时期,770-476 BC), in the State of Qi there was a man who always let his imagination run away with him.
春秋战国时期，杞国有个人喜欢胡思乱想。

One day he even worried that the sky would fall on his head. He was so worried that he could neither eat nor sleep.
一天，他竟然担忧天会塌下来，地会陷下去，自己无处存身。这个人越想越害怕，便整天愁眉苦脸，坐立不安，睡不好觉，吃不下饭。

Later, someone persuade him that his fears were groundless.
后来，有个人就去开导他，那个杞国人听后，才放下了心。

This idioms satirizes those who worry unnecessarily.
成语杞人忧天讥笑那些没有必要或毫无根据的忧虑。

【文化链接】

英文中“杞人忧天”可以用“Fear is often greater than the danger. ”来表达，直译也就是“恐惧往往已经超过了面临的危险”，这样讲就十分容易理解了~

动画片《老虎和兔子》的第四回的标题就是“Fear is often greater than the danger. ”而其中文译名就是“恐惧往往比危险更强大（与其杞人忧天、不如放手一搏）”。