You ought to keep your mind on what you are doing.

你应当专心致志地做你的工作。

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　　keep one's mind on:continue paying attention to 继续留神；继续专心于
　　再如:
　　It's hard to keep your mind on your work with all this noise going on.
　　这些噪声响个不停，很难使你专心工作。