Be on another planet; what planet is sb on?

Used to describe that sb's ideas are not realistic or practical (表示某人的想法完全不切实际)你在想什么啊,异想天开

He can't really think we're going to finish the job today, can he? What planet is he on? 他不是认为我们今天能把工作做完吧?真是异想天开.

Throw the baby out with the bath water: 把婴儿和洗澡水一起倒掉,把精华和糟粕一起丢掉

To lose sth that you want at the same time as you are trying to get rid of sth you do not want

It's stupid to say that the old system of management was all bad; there were some good things about it. The baby was thrown out with the bathwater.说旧的管理体制一无是处并不明智,它也有好的地方.那样说就相当于把精华和糟粕一同丢弃.

Throw in the towel/sponge: stop doing sth because you know you cannot succeed; admit defeat 放弃,认输,承认失败

It's a bit early to throw in the towel—you've only just started the job. 现在放弃为时尚早---你才刚刚开始这项工作.

这个习语源于拳击比赛:拳击手将毛巾或海绵扔下即表示认输.

This idiom comes from boxing: throwing in the towel or sponge is a sign that a fighter accepts defeat.