鱼哭了我知道我哭了谁知道
[yú kū le wŏ zhī dào wŏ kū le shéi zhī dào]
If the Fish Cries I Would Know, Who Else Would Know That I Am Crying. The user expresses their sadness and the feeling that only someone who truly knows them (like themselves or metaphorical fish) can understand such feelings.