西瓜不该知道柠檬的酸
[xī guā bù gāi zhī dào níng méng de suān]
Literally translates to 'Watermelon should not know the sourness of lemons'. It reflects on the notion that people from different walks of life (or situations) shouldn't experience (or don't understand) each other's pains and troubles. Here, watermelons symbolize comfort, while lemons symbolize difficulties.