feel blue 感到无精打采；心情不好；感觉不高兴；闷闷不乐

【例句】
There's no earthly reason for me to feel so blue.
我也说不出来为什么这么闷闷不乐。

As the only person who didn't make enough preparation for the moment, I'm totally in a mass and feel blue.
作为唯一一个没有做好充分准备的人，我完全陷入了一片混乱和忧郁之中。