这世界很小我们就这样遇见这世界很大分开就很难见面
[zhè shì jiè hĕn xiăo wŏ men jiù zhè yàng yù jiàn zhè shì jiè hĕn dà fēn kāi jiù hĕn nán jiàn miàn]
The world is small and we met so easily, but the world is vast and it’s hard to meet after parting. It expresses bittersweet feeling of meeting someone unexpectedly but finding it difficult to reunite.