You can't decide to stop caring what people think. You can see where your attention goes.
You've read the advice before. Stop caring what other people think. Live for yourself. Who cares what they say. It sounds clean on paper. Then you check the message again to see if she replied. You replay the meeting and wonder how you came across. You wear the second outfit because you don't want to seem like you're trying too hard.
The usual framing of "how to stop caring what people think" puts the problem in the wrong place. It treats caring as a choice you could cancel if you tried harder. It's not a choice. It's a loop running in the background, reading the room every few minutes, and handing you a stream of small adjustments before you've even noticed it's doing anything.
Why "how to not care what people think" is the wrong question
Attention isn't something you hand out on purpose. You don't wake up and assign three units of worry to your coworker's opinion. The attention goes there on its own, because at some point it was useful. Reading other people was a skill. It got you love, kept you safe, avoided conflict, earned approval. It worked. And now it won't quit.
Seeing where the attention goes is different from deciding not to care. It's slower and less heroic. The reward is that the loop quiets down a little once it knows it's being watched. The discomfort doesn't vanish, but the grip loosens.
What an autopilot actually looks like
An autopilot is a small chain of events: a trigger, an action, a quiet payoff. You see a notification (trigger), you check it immediately (action), and the uncertainty gets replaced by information (payoff). Harmless enough. Until you notice you've checked thirty times today and half of them were imagined notifications.
The autopilot around caring what people think works the same way. A small cue — a raised eyebrow, a delayed reply, a tone you can't read — triggers a scan. The scan looks for what you might have done, said, or not said. The payoff is the temporary relief of a plausible explanation, even when that explanation is worse than the silence it replaced.
Seeing the loop is what changes things
What you just did is closer to useful than any advice about how to stop caring. The loop didn't disappear, but it became an object you can look at instead of a weather system you live inside. That's the shift that actually lasts.
Attention loops around other people's opinions usually sit on top of something older — a rule that was handed to you and never renegotiated. To go further: looking at the rule underneath people pleasing.