There's a psychological mechanism, I've come to believe, that prevents most of us from imagining the moment of our own death. For if it were possible to imagine fully that instant of passing from consciousness to nonexistence, with all the attendant fear and humiliation of absolute helplessness, it would be very hard to live. It would be unbearably obvious that death is inscribed in everything that constitutes life, that any moment of your existence may be only a breath away from being the last. We would be continuously devastated by the magnitude of that inescapable fact. Still, as we mature into our mortality, we begin to gingerly dip our horror-tingling toes into the void, hoping that our mind will somehow ease itself into dying, that God or some other soothing opiate will remain available as we venture into the darkness of non-being.
It comes out from no source, it goes back in through no aperture. It has reality yet no place where it resides; it has duration yet no beginning or end. Something emerges, though through no aperture - this refers to the fact that it has reality. It has reality yet there is no place where it resides - this refers to the dimension of space. It has duration but no beginning or end - this refers to the dimension of time. There is life, there is death, there is a coming out, there is a going back in - yet in the coming out and going back its form is never seen. This is called the Heavenly Gate. The Heavenly Gate is nonbeing. The ten thousand things come forth from nonbeing. Being cannot create being out of being; inevitably it must come forth from nonbeing. Nonbeing is absolute nonbeing, and it is here that the sage hides himself.