Just a compilation of the replies from this post, because the forums won't let me edit it.

You know you play too much ArmA when...
... you shout out to your squad that you can hear a chopper, mashing Z to hit the deck. After spinning your character around a few times, you realise it's a chopper in real life.
... you only realised it was in real life because turning your character in-game couldn't locate the compass bearing of the sound.
... you start looking for ladders on the sides of buildings and sniping points.
... you view all stairwells as potential ambush sites.
... your pinky finger subconsciously extends for the PTT button, when your having an IRL conversation with someone.
... you're on a road trip and you're constantly scanning the horizon for hostiles.
... you're playing paintball/airsoft, and you think to yourself, "I wonder if there's CAS available for this mission... oh, wait."
... you are feeling sluggish or crappy and start thinking a reboot or defrag would make you feel better.
... you play a round of BF3 and go to revive a team-mate while spamming the ACE Interaction button and then can't figure out why you aren't getting them back up...yeah...that was a fun "moment".
... you enjoy walking to work 10 miles away.
... you suspect every pile of trash and dumpster is a possible IED.
... you try to mow your lawn with night vision goggles.
... you carry a compass around with you everywhere you go.
... you're out walking, and climb a small rocky outcrop. It overlooks a path down the valley. You think, "This would make a nice sniping position. The rock has nice cover, too... Shame about all the trees, though." Then realise you're not a sniper.
... you change your entire sleeping pattern so you can play with people in a different time zone.
... you're late for an interview because you spent 15 minutes at the trunk of your car making sure you have the exact brief case, pen and ink refills for the job.
... you perform a pace count around your house.
... you wish you had a friend to hold the line, while you flank around the mad shoppers to get your shopping and follow through.
... you methodically map out mentally an ingress and egress and the most effective avenues of approaches at the local super market to save time.
... you wish you had a recce unit to check ahead for traffic.
... you wish you had an interaction key to key cuff the ill mannered kids in public transport.
... you post in this thread.
... you play stalking games with your boy/girlfriend in a forest at night, and find yourself wishing you had a heat scope.
... you purposefully take a nap in the middle of the day to allow yourself to stay up to 4am playing ArmA with people in a different timezone.
... you are constantly over prepared for every possible situation.
... you wait for the chopper to come pick you up to transport you to your next transit point.
... you drive at "Q" speed when driving through small towns to keep your eyes open for IEDs and ambushers.
... too much ArmA when you get lost on the way home from uni in the middle of a strange city because you tried to avoid a broken down train, and don't panic in the slightest because you're not being shot at.
...you think of the territory you cover with your job as being roughly the size of Chernarus.
...you are performing a flanking maneuver on the cx (cx is short for customer) and are using bbm so they don't hear you direct (ie. "There is no way we are drilling out that tv outlet & wrapping their house....get out the 1" thick 2 foot long masonry bit & line it up on the baseboards and ask the cx if their shop vac will pick up water").
...you think the medivac helicopter landing at the nearby hospital needs a tail gunner.
...you have typed %appdata% into windows explorer this week and browsed your MPMissions cache..
...you are tired of people that don't have a clue they need a CLU.
...you will drive the atv from Rasman to Chak Chak (cross country) instead of mashing the respawn button because it will break your immersion.
...you are writing a work email and all words are made from the following keys W, S, A, D, X, C, F, E, Q, M, K & R - left click, left click, right click - blue in face... left click.
...you call a friend to pick you up from a train station because public transport is failing (gain) and think of it as "EVAC" / extraction.