旧人不及新人美新人不及旧人悲
[jiù rén bù jí xīn rén mĕi xīn rén bù jí jiù rén bēi]
This compares old lovers/friends ('old self') versus new loves/friends. New connections bring excitement, beauty, freshness, but the older relationships carried deeper sorrow or emotional weight because they carry memories and lessons of the past.