3 sentences

1. 妳今天晚上好像有点闷闷不乐。

   nǐ jīn​tiān wǎn​shang hǎo​xiàng yǒu​diǎn mèn​mèn​bù​lè.

   You seem a little subdued tonight.

   Source: OpenSubtitles

2. 她好像有什么心事，总是闷闷不乐。

   tā hǎo​xiàng yǒu shén​me xīn​shì, zǒng​shì mèn​mèn​bù​lè.

   She seems to have something on her mind; she's always moody.

   Source: Dong Chinese Dictionary

3. 自从考试没及格，他整天都闷闷不乐。

   zì​cóng kǎo​shì méi jí​gé, tā zhěng​tiān dōu mèn​mèn​bù​lè.

   Ever since he failed the exam, he has been depressed all day.

   Source: Dong Chinese Dictionary