不争气 [- zhēnɡ qì]be disappointing; fail to live up to sb's expectations; submit to defeat or failure without putting up a fight; be easily discouraged; let sb. down:
•¶ 他这个人真不争气。 This chap has let us down.
•¶ 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.