你是我心底经久不散的秘密
[nĭ shì wŏ xīn dĭ jīng jiŭ bù sàn de mì mì]
'You are the secret lingering in my heart.' This signifies a person or experience remains as hidden love, admiration, crush, regret etc. cherished privately and kept undisclosed by oneself for various reasons ranging between privacy, social pressure or simply timing