The following adjectives all have the meaning of 氣餒的, 沮喪的, 意志消沉的, 心灰意冷的.
Down in the mouth
Sad and gloomy
I would say a more commonly used word by the Americans is “depressed”, “down” or “downcast”.
John felt so down this morning and almost committed suicide.
John felt so depressed this morning and was at the verge of committing suicide.
John felt so downcast this morning and almost gave up his life.
Frustrated means disappointed, which means more about 受挫的, 失望的.
Myself. Went abroad at age 11. With 32 years experience speaking and writing English. Tutored English as an Undergrad. A project manager in the US since 1992.