彼时自失
[bĭ shí zì shī]
'彼时'(bi shi) refers to 'that time', and '自失' (zi shi) can mean losing oneself. So '彼时自失' can refer to those moments when people feel lost or out of place, as if they are not truly living in the current time, or missing past times. It implies someone feeling disconnected from the current moment or reminiscing about the past, often associated with feelings of regret or longing.