One must draw the line somewhere. 人之所为，总有限度。
One must drink as one brews. 自作自受。
One must howl with the wolves. 入乡随俗。
One never loses anything by politeness. 有礼貌对自己不会吃亏。
One never loses by doing a good turn. 行善者决无一失。
One penny witgh right is better than a thousand without right. 合法得来一个钱，胜过非法钱一千。
One ploughs, another sow; who will reap no one knows. 有的耕，有的播，谁来收获很难说。
One rotten apple spoils the whole barrel. 一只烂苹果烂一萝苹果。
One should eat to live, not live to eat. 人为生而食，非为食而生。
One sin opens the door for another. 一个罪恶常为另一个罪恶开门。
楼主