阅读下面材料，在空白处填入适当的内容(1个单词)或括号内单词的正确形式。
(2015·青岛市二模)
It's never foolish __1__(acknowledge) you are in the wrong. Being human, we all need the art of apology. Look back and think how often you've judged __2__(rough), said unkind things, pushed yourself ahead __3__ the cost of a friend. Some deep thought lets us know that when even a small mistake has been made, your feeling will stay out of balance __4__ the mistake is acknowledged and your regret is expressed.
