First day back…

Today's the first day back at school or work for many of you in Europe after the Christmas / New Year holidays. So my question's really for you:

-What's the most difficult thing about going back to school or work after three weeks off?

Getting up in the morning?
Adjusting to a new routine?
Not being able to do the things you want to do when you want to do them?

Hope it's not too bad a day for you all!