今生只为你展开笑容今世只为你默然心情
[jīn shēng zhĭ wéi nĭ zhăn kāi xiào róng jīn shì zhĭ wéi nĭ mò rán xīn qíng]
It expresses a lifetime of smiling just for one special person alongside silently harboring one's deepest affections toward them throughout this life - dedicating all joy and melancholy exclusively towards that individual.