Vacation amnesia refers to this situation: when you come back to school or work from your vacation, you can't remember what you did before the vacation. Things you can't remember may include: what project you were working on, any paper needed to be finished, or even who was taking care of your business when you were on vacation.

“假期失忆症”指的是这样一种情况：你度完假回到学校或单位后发现已经完全不记得度假之前你在做的事情。你当时正在进行的项目、有需要完成的论文、甚至度假时谁接手了你的工作都有可能不记得了。

For example:

Andy suffered from a bad case of vacation amnesia when he went back to school and couldn't remember what he had been learning before.

安迪得了严重的“假期失忆症”，他回到学校后根本不记得之前都学过些什么。