lit. once you've shot the arrow, there's no getting it back (idiom); fig. once you started sth, there's no turning back; to have to finish what one started; to be determined to reach one's goals in spite of setbacks
trad. 開弓沒有回頭箭
Also written 開弓沒有回頭箭【kāi gōng méi yǒu huí tóu jiàn】