Believe it or not, they knew about your mood long before you returned from the fridge, flopped on the couch and let out that long, beer-tainted sigh. It's another defense mechanism (notice a pattern here?) that they picked up years before they even knew of your existence. When Mom or Dad's moods started to fluctuate, bad shit happened. Over time, the kids learned that those moods always had telltale signs that predicted their eruptions. Ash that preceded the lava.
At first you take notice, even if it's subconsciously, that before Dad explodes, he starts rubbing his temples. Big, obvious things like that. But over time, you can't help but pick up on more subtle signs. He lets out a very soft sigh when it's going to be just a quick stick-and-move belittling session. He fidgets with his lighter when it's going to be a really bad one. The skill is developed so that when you see it happening, you can either brace yourself for the train wreck, or you can make yourself scarce so you don't have to deal with it.
Just like any skill, the more you use it, the better you get. Over the years, it becomes so woven into the fabric of your personality, you couldn't remove it without completely breaking down who you are as a person and rebuilding the cloth from scratch. So it's rarely ever a case of the person just trying to smother their partner with attention out of some sense of insecurity. It's force of habit. Alarms are going off in their subconscious that shit is about to hit the fan, and they need to defuse that bomb before it goes off. And anything can trip the alarm. The slightest change in tone of voice. The most subtle shift in eyebrows before you speak. The way you're standing. A simple change in your daily routine. The subtle way you look them in the eyes and say, "I'm about to physically punch you directly in the face with my fist. Here I go."
It sounds like a damn superpower, but it can be a real problem in relationships, because the constant questioning and attempts to fix the other person's bad mood can be suffocating. Every person needs to be allowed room to vent their stress and frustrations, but that thought scares the ever-loving shit out of the person who lived through a dysfunctional family. Because he's used to those very things being followed by aggression and hate.
- John Cheese
descensus Averno facilis est