I have no use for the sad sack of a man.

叫他走吧，我不要这个不中用的人。

There is no room for such sad sack of man.

这里不需要如此一无是处的人。

The blobfish is practically all face — a pale, gelatinous deep-sea creature whose large-lipped, sad-sack expression seems to be melting toward the floor.

水滴鱼实际上全身都是一张脸，这种苍白、胶状的深海生物长有大大的嘴唇，忧郁的表情似乎马上就要融化在地板上。

Are you a little tired of seeing the same sad-sack faces month in and month out?

每个月都看到同样一脸倒霉相的人，有点烦是吧？

John is sad because he just got the sack from his girl.

约翰很伤心，因为他与女朋友吹了。