清风似水流年忘返微雨似箭流年追忆
[qīng fēng sì shuĭ liú nián wàng făn wēi yŭ sì jiàn liú nián zhuī yì]
It roughly means 'The gentle breeze like water flow through years unnoticed; light drizzle resembles arrows piercing memories.' This conveys how some pleasant moments slip away quietly but painful experiences stay sharply remembered.