鱼忘七秒人念七年
[yú wàng qī miăo rén niàn qī nián]
The phrase translates to 'fish forget in seven seconds while humans remember for seven years.' Fish are commonly believed to have only a few seconds of memory; this is contrasted with humans who can't easily let go, possibly alluding to long-lasting memories (or regrets). It speaks to the difference between how quickly fish forget and humans tend to dwell on emotions, especially those bittersweet ones.