Whenever you want to express something like "you did it again!" in Chinese, you may want to use 又. It is Expressing time and date, Referring to the past.

Structure
There are two words for "again" in Chinese. This depends on whether the repetition has happened, or whether it's going to happen. If the repetition has happened, i.e. it's a repetition in the past, 又 is used.

subject+又+verb+了

Notice that 了 is used as the action is complete. 

Examples