You actually teach someone the (alleged) idiom, "It's raining cats and dogs."
You start making the same errors as your students.
When you use the letters BC (which you do far too often, by the way), you're not even referring to a period of time.
You appear on promotional materials for your shitty, low-paying school with a grin that looks like you've just received a Botox injection from the dustbag of a Dyson.
You don't fear people observing your lessons; they fear you.
Students in ex-Communist states laugh pityingly at your salary.
You save money by walking metro stops, shopping in food stores right before they close and sleeping overnight in parks.
You've found a way of getting two meals for the price of one by buying jam tarts, only eating the pastry and scraping what's left onto a slice of bread later as a treat.
You've actually had a 'proper job' and then gone back to TEFL.
Your friends no longer ask when you're "going to settle down and stop running away" but only because you've lost all their contact details.
You become embroiled in a staff room argument about the existence of a future tense in English. "I'll smack you one in a minute." "Yes, but you're still threatening me from a present aspect."
You love the sound of your own voice and often find yourself talking to people without actually caring whether they're a) responding, b) listening or c) interested in what you have to say.
You write up the above in multiple-choice format and use it as a listening comprehension test for your next conversation.
You turn into your least favourite teacher from school.