Your body continuously flows and dissolves. If the food you eat had not been digested and dissolved, and had not left your body, and if its quantity had been added to your material form, your body would have become immense. Your body is in continuous decomposition. If this continuous birth and death did not occur in your body, and your cells multiplied, your form would have been the size of a giant.
That which is constant, always alive, indivisible, is the opposite of that which changes, divides, dissolves. The essence, the one "I" in your declaration of "I am," is one indivisible, constant and eternal. Therefore, your essence is incorporeal, and cannot be a part of a material being.
As long as your essence is realized within you in a constant state, you are you forever, while with this body you are not. It changes, it is decomposing, it is dying; you don't know it, you don't feel it. How could you be that body? You are much more than that. Allah says in His Holy Book, the Qur'an:
But Allah has encompassed them from all sides. (Al-Burj 20)