be modest about one’s talent (/learning); not be given to boasting (/showing off)
? 這位年輕人～，將來一定很有出息。This young man is always modest about his learning. He is sure to have a bright future.
深藏若虛shēn cánɡ ruò xū
虛：空。深深地隱藏著，好像什么也沒有。比喻身懷真才實學的人不在別人面前顯露。be modest about one’s talent or learning, not be given to boasting or showing off, hide one’s light under a bushel