You must never do this.

这件事你做不得。

《新英汉大辞典》

I'll never repeat this one enough, getting out of your regular stuff is something you MUST be able to do by yourself.

做常规事务以外的事应该是你的必备能力，这一点永远值得重申。

youdao

Everyone to achieve their dreams, must pay for this. One pay, one obtained. If you do not pay, but only where fantasy you will never be reached.

每个人要达成自己的梦想，必须为这一方面有所付出，因为只有付出，才会有所得，如果你不付出，而只是在那里空想，是永远都不会达成的。

youdao

And so the big issue is -- this is what you must never do, but this is what you got to do if your phalanx is broken.

所以现在的大问题是,这也许是你在战场上永远不能做的事,但你在方阵被打散时不得不这么干

耶鲁公开课 - 古希腊历史简介课程节选