嘴里依旧哼着的低调嘴里依旧上扬的微笑
[zuĭ lĭ yī jiù hēng zhe de dī diào zuĭ lĭ yī jiù shàng yáng de wēi xiào]
'Still Humming Quietly While Still Smiling’. This conveys a sense of maintaining a modest and unassuming demeanor outwardly while keeping a genuine joy internally expressed only by oneself in form of hums and barely noticeable smile.