You can spot incorrect grammar and spelling a mile off.
You can make up games on the spot.
You realise there are never enough pencils/gluesticks/scissors in the world.
You see a child misbehaving in the supermarket you automatically give them "the look".
You have perfected "the look" which turns any child to stone.
You find yourself clicking at blank pages hoping this will make a child's work magically appear.
You are immune to the smell of farts and urine.  
A social life was a thing you used to have.
Weekends are spent planning for next week, holidays are spent writing reports.
You can't remember the last time you blow dried or straightened your hair.
You can maintain a straight face in ANY situation.
You soon realised that although school hours are 8.30-3.30, your day begins at 6am and finishes at 10pm.
Also, you realise some names you will never name your own children, due to experiences with children who have that name!
Tea and Coffee are your life.
The staffroom is your sanctuary.
Packed lunches are a part of daily life.
You want to choke a person when they say "Oh, you must have such FUN everyday. This must be like playtime for you."
You also want to stab any person who says the following with a compass "Teaching? That's just about learning how to write on a whiteboard right?"
You can sense misbehaviour without actually seeing it.
The sound of the photocopier haunts you in your sleep.
When a lunchtime supervisor/helper/ta comes into your class to complain openly about them, you find yourself saying "OH dear, how sad" in an overly dramatic way!
You say things once, then repeat them, then ask if everyone understands what you are saying, before repeating again.
When you are out shopping in the town of your school you are greeted with at least five cries of "Hi Miss/Mr!!"
You don't bother telling people anything about your job as they never seem to fully understand the stress...(sigh)
You count down the days till half-terms, holidays, bank holidays, weekends knowing that without them you would be headed for a nervous breakdown.
You have more control over/respect from children than their parents.
When you meet someone else who is a teacher, you have an immediate bond.
You still get nervous about class assemblies.
You loathe children who finish their work quickly!
Stickers are still a form of excitement for you (especially scratch n sniff ones!)