2 sentences for 没劲 (méi​jìn)

1. 由于感冒，我今天觉得全身没劲。

   yóu​yú gǎn​mào, wǒ jīn​tiān jué​de quán​shēn méi​jìn.

   Because of a cold, I feel weak all over today.

   Source: Dong Chinese Dictionary

2. 大家都走了，一个人在这儿待着真没劲。

   dà​jiā dōu zǒu le, yī gè rén zài zhè​r dāi zhe zhēn méi​jìn.

   Everyone's gone; it's really boring staying here alone.

   Source: Dong Chinese Dictionary