I'm no psychologist, but it is fairly common knowledge that grief is a natural part of life, if we conceive of it broadly as going through the process of psychologically dealing with loss. Loss is natural and ubiquitous if one is alive, growing, or changing... all the time one loses one's former self to become something new , something more (or different), a process of being is not static - it is a process of becoming.
We transform from a dependent child to an adult, we learn to accept that Santa Claus is a fiction, as an adult we accept "the highschool years" as a part of our ever evolving lives and not its definition, and we must learn to make the transformation through old age and decline as well... These transformations and the subsequent introspections of the differences of self, require a process to fully deal with.
We are aware that those who do not properly process these changes, as with those who do not properly process the death of a loved one, have psychologically unresolved issues... which can and will be problematic, until they are properly processed and there is closure and acceptance of the reality of that particular loss or change on a deep psychological level.
One of the biggest psychological transformations a person can go through is to convert from an adherent of the religious/supernatural/mystical to a complete atheist. This is no trifle... it is a fundamental shift of a world view, indeed a view of the universe, all of existence, its relation to the self and the very definition of self also.
Is anyone aware of any authority, academic, or psychologist who delved into, contemplated, and/or wrote substantively on the subject matter of the psychological process of Grief necessary for fully completing the transformation from religion to atheism in a psychologically healthy manner?