杞人忧天（杞人憂天）　

◎ 杞人忧天 qǐrén-yōutiān

(1) [like the man of Qi who was haunted by the fear that the sky might fall]∶《列子·天瑞》:“杞国有人忧天地崩坠,身亡所寄,废寝食者”。传说杞国有个人怕天塌下来,愁得寝食不安

(2) [with unwarranted anxiety]∶比喻不必要的忧虑