碰钉子

bù chéng shí de rén fēi pèng dīng zi bù kě

不诚实的人非碰钉子不可。

A dishonest person is bound to meet with setbacks sooner or later.

jiǎ rú nǐ bù xiǎng pèng dīng zi jiù bié qù qiú tā bāng máng

假如你不想碰钉子，就别去求她帮忙。

If you don't want to be brushed off, forget about asking her to give you a hand.