西瓜不凉心却凉了
[xī guā bù liáng xīn què liáng le]
This phrase can be literally translated as 'Although the watermelon is not cold, my heart has become cold.' In Chinese culture, cold melon is a popular snack on hot summer days, and here it symbolizes that although objective conditions (watermelon) have not changed, one's mood or attitude may have cooled down due to something unfortunate.