世上最痛苦的事是不能睡觉
[shì shàng zuì tòng kŭ de shì shì bù néng shuì jué]
'The most painful thing in the world is not being able to sleep' - this implies insomnia or severe stress which prevents one from getting peaceful rest. Sleep here signifies peace and tranquility; lacking it means suffering greatly both physically and mentally.