不争气

wǒ zhè tuǐ bù zhēng qì zuì hòu yī quān pǎo bù dòng le

我这腿不争气，最后一圈跑不动了。

My legs failed me and I wasn't able to run the last lap.

tā de ér zi bù zhēng qì

他的儿子不争气。

His son let him down.

tā zhè rén zhēn bù zhēng qì

他这人真不争气。

This chap has let us down.