笑到心酸笑到心痛
[xiào dào xīn suān xiào dào xīn tòng]
'Laughing until I'm choked with emotion, laughing until my heart hurts.' It conveys complex feelings, especially bitter sorrow or anguish covered under forced smiles, which might come from pretending happiness when actually enduring deep inner pain, often related to poignant experiences of life.