表面大大咧咧内心却是伤感
[biăo miàn dà dà liĕ liĕ nèi xīn què shì shāng găn]
Translating as 'Outwardly Uninhibited But Inwardly Sentimental', it conveys the idea of being carefree or even careless on the surface, but harboring deep and sensitive emotions within.