再见说的那么轻就好像空气
[zài jiàn shuō de nèi me qīng jiù hăo xiàng kōng qì]
Saying goodbye can sometimes be too easy-going like air, not heavy enough to be felt, which might reflect a feeling of sadness when bidding farewell or the difficulty of keeping in touch once a friend departs far, expressing unexpressed sorrow and longing.