There's this place up above the universe.
It floats around filled with souls. It's a factory of some sorts with the angels as its workers. They sit at this golden conveyor belt that spits out bodies, and they stick the souls in them. After the souls have been placed inside, they flip some switches. Some switches make you athletic, some make you artistic. Then they press some buttons. These buttons give your life on Earth purpose.
After that, your body is sent down to Earth to live its programmed life.
But sometimes, when the angels switch shifts, a body slips by. No switches are flipped and no buttons are pressed. It gets sent down to earth with no purpose or meaning.
After awhile this body become self aware. It realizes it does not fit. When this happens the body will then self destruct. The discarded body, now covered in cuts deeper than the heavens, will become one with the earth where it will rest until the factory of the universe shuts down.