Finding her in low spirits, they had persuaded her to join them for lunch.
他們發現她情緒低落, 便勸說她同他們壹塊兒吃午飯.
來自《簡明英漢詞典》
2. During breakfast those disembarking were in low spirits. 吃早飯時,今天下船的那幾位都垂頭喪氣.
來自漢英文學 - 圍城
in high spirits
興高采烈；起勁；心情歡暢；帶勁
At supper, everyone was in high spirits.
晚餐時，每個人都興致勃勃。
來自柯林斯例句
二、spirit表示“某種精神”或“精神實質”時,是可數名詞。所以in low spirits最好加上s。