3 sentences

1. 做人得凭心眼，不能干那种亏心事。

   zuò​rén děi píng xīn​yǎn, bù néng gàn nà zhǒng kuī​xīn​shì.

   One should live with a conscience and not do things that go against it.

   Source: Dong Chinese Dictionary

2. 他做人一向坦荡，从不背人做亏心事。

   tā zuò​rén yī​xiàng tǎn​dàng, cóng bù bèi​rén zuò kuī​xīn​shì.

   He has always been an upright person and never does anything shameful behind people's backs.

   Source: Dong Chinese Dictionary

3. 只要没做亏心事，他的心里就会很坦。

   zhǐ​yào méi zuò kuī​xīn​shì, tā de xīn​li jiù huì hěn tǎn.

   As long as he hasn't done anything against his conscience, he feels at ease.

   Source: Dong Chinese Dictionary