When it's the first day back to class after Christmas break.
When you walk into your classroom and it is already almost completely full.
"Let's go around the room and introduce ourselves to everyone."
"I'm assuming you have all read the first 56 pages of the textbook."
"I'm assuming you all remember this from your previous classes in this field."
"Just go ahead and finish all 8 of these worksheets by Wednesday."
When all of your classes indicate that they are going to be a lot harder than you anticipated.
When someone starts a conversation about a controversial topic on the first day.
When you schedule enough time between your classes for a nap.
When you walk out of your last class of the day..
..Then you remember how much homework you have to do by 11:59.
