This old exercise is one of my favorites. It never fails to leave me feeling a little more sane. It is not proof of anything, just a means of having an experience. We confuse so many strange and silly things with our identity, our self, that any trick we use to sort ourselves out can be an aid to our happiness.
Sit comfortably, close your eyes, and begin slowly asking yourself, "Where am I?"
Follow by asking yourself, "Am I in my hair?" "Am I in my eyes?" "Am I in my head?" "Am I in my brain?" "Am I in my shoulders?" In an easy and pleasant way, continue down the body with similar questions, pausing after each one for a gentle sense of the answer. "Am I in my torso?" "Am I in my heart?" "Am I in my hips?" — and so forth, making the questions as general or detailed as you wish.
When you have finished you will probably have an increased awareness of that part of you that is always you, regardless of age, haircuts, amputations, prostheses, brain damage, or any other bodily changes. This awareness may be quite strong.
— Hugh Prather in How to Live in the World and Still Be Happy