一种相思两种情愁
[yī zhŏng xiāng sī liăng zhŏng qíng chóu]
Directly translating into 'One Love Two Sorrowful Feelings'. It seems this refers to limerence where the yearning from longing is felt deeply by both involved yet tinged with distress, probably because they are unreciprocated feelings or there're troubles in the relationship.