心如冰块自然凉心如柠檬自然酸
[xīn rú bīng kuài zì rán liáng xīn rú níng méng zì rán suān]
The phrase means 'A heart like an ice cube feels naturally cool; A heart like a lemon feels naturally sour.' Here 'a heart like an icecube (a cold-hearted)' describes a person's calm, indifference or numbness whereas 'heart like a lemon' expresses someone might have been disappointed or suffered pain from some unhappy events.