1. That proved to be my undoing, for I soon got back to my old bad habit of dozing off in front of the screen.
    这证明了我的失败，因为我不久就回到电视屏幕前打瞌睡的坏习惯去了。

2. That proved to be my undoing, for I soon got back to my old bad habit of dozing off in front of the screen.
    这下我可完了，因为不一会儿，我就恢复了以前的坏习惯，在屏幕前打起瞌睡来。

3. To study his image in the sight of those who do not know him, can be his undoing: he has begun to write to please.
    企图用不了解自己的人的观点来研究自己塑造的形象的作法，会导致作家的毁灭，因为他已经开始为取悦他人而写作了。