猫忘了鱼尾纹鱼忘了旧伤疤
[māo wàng le yú wĕi wén yú wàng le jiù shāng bā]
A metaphorical way of expressing that one has forgotten sorrows and pains just as a cat wouldn't care about its wrinkles and a fish wouldn't remember its old wounds. A light-hearted portrayal of forgetfulness or letting go of past issues.