L.S.
Before kids I slept on the side farthest from the door so if an intruder came in, he'd have to go through my husband first (HIS reasoning, not mine!)
Now, after kids, I sleep closest to the door so the kids reach me before my husband (MY reasoning).
As for not being able to sleep unless I'm on "my" side, after dealing with 3 kids under 5 all day I could probably sleep in the tub if I had to!