You know when your head starts running the show.
You overthink your next line. Judge yourself while you're still speaking. Second-guess the point you were about to make. Memorize every word because you don't trust yourself to speak into the moment. Play it safe, soften your message, or try so hard to get it right that the room never gets the full force of you.
Without Walls changes who's leading. Your core essence, the message and feeling behind it, your voice, style, soul, and energy come forward. You can think on your feet, speak off the top of your head, respond to the room, and let the moment lead without losing yourself.
The switch comes through experience. Think of learning to ride a bike: once your body finds the balance, you know how to find it again, even years later. The walls may still show up, but they don't have to run the show. You know how to return to that place where the full power of you is available.