When one existentially awakens from within, the relation of birth-and-death is not seen as a sequential change from the former to the latter. Rather, living as it is, is no more than dying, and at the same time there is no living separate from dying. This means that life itself is death and death itself is life. That is, we do not shift sequentially from birth to death, but undergo living-dying in each and every moment.
A Study of Dogen: His Philosophy and Religion (ed. SUNY Press, 1992) - ISBN: 9780791408377