Whenever you catch yourself thinking that you do not want some thing or a thought, you can then say, "Oh, I know what I do not want."

无论何时，只要你发现自己在想自己的想要的东西或想法，你就可以对自己说：“哦，我知道我不想要的是什么了。”

youdao

I was that scared I didn't know what to do.

我非常害怕，以至不知如何是好。

《牛津词典》

I was out of my mind with fear. I didn't know what to do.

我害怕极了。我不知道该怎么办。

《柯林斯英汉双解大词典》

I do not know what else to do but make the best of a bad deal and shake hands over it."

VOA: special.2009.06.27

And then the last thing I want to do, is just decide, you know, what do I do when I'm done.

决定，你知道的，当我完成循环后去做什么。

麻省理工公开课 - 计算机科学及编程导论课程节选

I chose English Literature because when I started off a university, I didn't know what it was I wanted to do.

我选英语文学是因为当我刚上大学的时候，我不知道自己到底想做什么。

为何选那门专业？ - SpeakingMax英语口语达人

But I know the first -- what I would do -- I know what I would do the first hour that I was president.

CNN: Thompson's October 19, 2007, speech to Value Voters Summit

"If I don't get in the squad I don't know what I will do, " said 31-year-old Bellamy, who revealed he has rejected an offer to join German club Wolfsburg.

BBC: Craig Bellamy talks of quitting football

If I was one of them, I don't know what I'd do.

ECONOMIST: Interactive television