她不是我怎懂你心他不是我怎入你心
[tā bù shì wŏ zĕn dŏng nĭ xīn tā bù shì wŏ zĕn rù nĭ xīn]
'If she is not me, how can she understand your heart? If he is not me, how can he enter your heart?' This conveys a sense of exclusiveness and uniqueness in someone's relationship or bond with another person.