The tradition of the Providence Zen Center (PZC) is to always ask yourself, “What am I?” This is a way of maintaining your concentration on the present moment. One variation of this is that when you breathe in as you meditate you should think, “What am I?,” and as you breathe out you think, “Don’t know...”
Another variation is that when you’re doing something active you should incorporate your activity, so when you’re walking you ask, “Who is walking?,” when you’re driving you ask, “Who is driving?,” and so on.
One day I was at the PZC, taking a shower, and asking myself repeatedly, “Who is showering? Who is showering?” During this time someone knocked on the door and yelled, “Who’s in there?”
Instinctively I answered, “Don’t know!”
Then they yelled louder, “WHO’S IN THERE?”
I yelled back, “DON’T KNOW!”
They went away after that. I never did find out if they were testing me again, or actually looking for someone.