三秒梦三年疼七年忘七年痒
[sān miăo mèng sān nián téng qī nián wàng qī nián yăng]
An emotional expression that compares the briefness of moments (like a 3-second dream) to the prolonged feelings it leaves behind, such as pain and longing. It's a poetic way of expressing the bittersweet aspect of memories.