While I do not believe you need to be religious to discover that you have a spirit, or that you are a spirit, dwelling within the machine called the human body; I too have experienced such an experience too. No one is alone in such experiences, as my discovery was very simple at first, there are many realms and more dimensions beyond the four used to measure the modern societal apparatuses of our economy and ecology. From my experience I learned that this body holding me is a vessel that is directed by a spirit to perform in the livelihood of an avatar carnated for some divine purpose, understood or not, by the fates themselves.
While this is not an empirical response or the final conclusive response to the reason our spirits sometimes detatch from the corporeal and mind, I believe it to be relatively decent in explaining a part of how our spirit sparks the animation of life.
I will now always view the body as a machine to be taken care of and cared for as it is perhaps the most important tool to discovery and interaction with those of whom remain animated on this planet (and beyond). I see the underlying role of life's purpose to be the establishment and actuation of the sphere of order thereby protecting all life from the hazards of the sphere of entropy. From my OBE and NDE I believe that order is why we each are animated in the persistance to sustain and stabilize the sphere we live on as one in the likeness of the sphere of order. I have also shed my belief in death and believe that the cessation of the body to be no more than the spirit detatching from the vessel to move on to the next stage of life to reside as captain of the next avatar... perhaps granted by the fates and/or the deities (or deity) that you worship as the divine parent spirit above (father or mother).