英语听力课堂(www.tingclass.net)是公益性质的英语学习网站，您可以在线学习英语听力和英语口语等,请帮助我们多多宣传，谢谢！
to stop being careful to avoid danger or difficulty
放松警惕
Once he knew I wasn't a journalist, he dropped his guard and even let me take a photograph of him.
当他知道我不是记者的时候，他立刻放松了警惕，甚至让我为他照相。
It's normal enough to drop your guard when you have reached a great objective.
当你完成一个重要任务后，总是会丧失警惕性，这很正常。