Some years ago, I picked up a contract with a company. My first day there, one of the guys offered to show me around. As we went down a long hallway, I noticed we were in step. When we came to the end of the hallway, we both took a little halfstep and scanned the opening and the room we were entering. I turned to him and asked, "Special Forces?" He replied, "Force Recon. And you?" I replied, "SAS." We got along fine.
I have many of the same habits described here. I'm not obsessive about them but they make me feel more comfortable. My wife and kids have the same awareness and that makes me feel more comfortable, too.
I once took a friend who always insisted on sitting with his back to a wall and facing the door to a little Greek restaurant I had found. It was basically a long room, with a door to the outside on each end. You couldn't sit without having one of the doors at your back. Neither one of us was ever able to eat there without the other along.
Pops