Watching what you say and what you do isn’t masking. Watching what you are is masking. You don’t just filter out, you have to emote entire emotions that you’d express entirely differently because other people are disturbed by your normal expression of XYZ feeling.
It comes from years of being double punished when something bad happens because our remorse facial expression doesn’t match what they think remorse is supposed to look like so they don’t see any. And sometimes those.punishments are just for expressing something else in the non standard way.
I mean sure filtering topics is part of it, and it often involves filtering very pertinent topics. For example if something is really bothering you to the point of physical pain, but it isn’t supposed to be bothering you, that is the topic you then have to filter. And you have to physically replace your expressions of pain with whatever emotion you are supposed to be feeling. Of course you don’t replace your pain with the way youd express the emotion you’re supposed to be feeling. You replace the pain with how they wish you’d express the emotion they wish you’d be feeling.
Masking is gaslighting your entire body and brain out of every big and small action and reaction until whoever it is you really are is difficult to even retrieve.