Why do I care so much about what people think?
You care so much about what people think because somewhere along the way, other people's reactions became your main source of information about whether you were safe, good, or acceptable. It is not vanity. It is a tracking system that got installed early and never got updated.
The system you're actually running
Underneath the worry about what people think is a much older, faster process: scanning faces, tones, and silences for signs of danger or disapproval. If you grew up in a house where a parent's mood could shift the whole room, or where love arrived with conditions attached, you learned to read the room before you learned to read a book. That skill did not turn off when you left the house. It just started running on coworkers, partners, strangers on the internet, anyone whose face you can see. You are not insecure. You are pattern-matching against a threat detector that used to be accurate and is now firing on people who genuinely do not matter.
Why this makes complete sense
For most of human history, being cast out of the group was a survival-level event, not a social one. Your brain still treats disapproval like exile. If you were also the kind of kid who got praised for being easy, agreeable, or impressive, you learned a second lesson on top of the first: your worth was a performance review, not a fact. Both of those are reasonable adaptations to real conditions. The problem is not that you developed this. The problem is that it never got a chance to recalibrate once the actual danger passed. A grown adult with a stable job and people who love them can still feel eight years old when a text goes unanswered for six hours.
The tell that gives it away
Notice who you actually spiral about. It is rarely everyone equally. It is usually the person who reminds you, even slightly, of someone whose approval used to be unpredictable, someone withheld, someone critical, someone you had to earn your place with. A stranger's neutral face on the subway does not cost you anything. Your boss's neutral face after you spoke up in a meeting can ruin your afternoon. That gap is the clue. It is not about how important the person is objectively, it is about what their reaction used to mean for your safety in an earlier version of your life.
What actually helps
Reassurance does not fix this, because the fear was never really about logic. What helps is building a track record with yourself, not with them. The next time you catch the spiral starting, name the actual prediction out loud, specifically: I think they are annoyed with me and that means I did something wrong. Then wait and check it against what actually happens. Most predictions do not come true, and the ones that do rarely mean what you feared they meant. Do this enough times and the tracking system slowly gets new data. You are not trying to stop caring. You are trying to teach your nervous system that this particular room is not the one it thinks it is.
When this runs your life, it usually traces to one underlying pattern. For this, it is most often the Mirror rhythm, the thing under the behavior.