咬紧牙关完成这件事吧: you just bite the bullet and get it over with
不服: refuse to obey; not give in to; recalcitrate; refuse to accept as final; remain unconvinced by 短语和例子不服裁判 refuse to accept the referee's ruling; 不服从 disobey; 不服老 refuse to give in to old ag
心中不服: a lack of hearty support; be mutinous in one's heart