思念是一座围城
[sī niàn shì yī zuò wéi chéng]
Drawing on Qian Zhongshu’s famous analogy in Fortress Besieged (《围城》), this translates to 'Longing is a besieged city' symbolically representing that love or memories are like a besieged city; you wish to leave it when you're inside but yearn to go back once outside.