没心没肺狼心狗肺
[méi xīn méi fèi láng xīn gŏu fèi]
Although the literal translation might seem like someone without feelings or compassion, in colloquial Chinese, it expresses someone who has learned not to be hurt anymore through being emotionally 'guarded'. However, if taken as 'wolfish and dog-hearted,' it would represent cunning and insincerity but should consider the actual context in which this idiom is used.