Wiktionary
down in the dumps
a. (context idiomatic English) sad; lacking engagement or enthusiasm.
Wikipedia
Down in the Dumps
Down in the Dumps is a 1996 computer adventure game developed for MS-DOS and Microsoft Windows, by the French Haiku Studios and published by Philips Media. The release for Apple Macintosh was published in 1997. Versions for the PlayStation, Sega Saturn and Philips CD-i were slated for 1996, but never released.
Usage examples of "down in the dumps".
Donnie was down in the dumps, and not just from the humiliation at the hands of them hippies, neither.
Before he was hurt, I had known why I was down in the dumps: it was because he was going and I wasn't.
You certainly have - what else do you suppose put me so far down in the dumps?