When im out of body sometimes I can feel the bridge of my nose. I also think of myself haveing an experience inside my head so that makes the experience end. I do notice that if I dont think of my body while out of body it lasts longer. I dont think astral projection made possible only by your brain, I think the portal to that dimension is in your brain.
I don't know if there's a way you can completely block out the feeling from your physical body, after all you are still attached/there.