It requires concentration. The picture has to be clear in my head; I have to be able to feel my body coming into compliance with it as I make the change. It's taken years of practice to be truly convincing. Details matter.
When I'm ready, I can step out into the open grass and onto the sidewalk and across the road and up the steps and ring the doorbell. I can hold my hat and smile and mention familiar and trustworthy names. I can sit in the parlor and sip tea and enquire after health.
The anticipation builds the appetite.