Confidence that needs an audience is still nervous.

The loud kind of confidence is often a question being asked over and over: is this working, do you see me, am I right. It needs a reaction to stay upright, so it grows in a crowd and vanishes when nobody is around to watch. Real steadiness is quieter, because it is not waiting to hear back from anyone.

Notice what you do with no audience: how you practice, how you talk about people who are not in the room, whether you still care with nobody to tell. That version is the actual measurement. Build it, and the outward part stops having to work so hard.