Both MJM and OnMyOwnTwoFeet have written before about Pauline Boss's concept of "ambiguous loss," a term Boss coined to describe the grief of those who have lost loved ones and have no closure--soldiers MIA, runaways whose fates remain unknown, etc. 

 I am currently reading the book "Soul Broken: A Guidebook for Your Journey Through Ambiguous Grief," and thought both the concept and the book might be useful to others.  "Ambiguous grief" is a concept that builds on Boss's work, but in this case the loved one is alive but there's been a change or break in the relationship, whether from dementia, mental illness, a disclosure or discovery of a competing sexuality and/or gender identity.  We have "lost" the person we knew, and grieve the loss, but the person remains. (Women in my situation--husbands who declare they're women in men's bodies--are even known as "transwidows," because it's as if our husbands have died, even though they go on living, but not as the husbands we knew them as.) 

 It's a pop psych book, but I'm finding it helpful nonetheless.  She highlights ideas of the "activating event" (the discovery or disclosure, which is the beginning of the rupture), and guides one through useful strategies for dealing with the loss, including "intentionality," and the different aspects hope, wither internal (self-directed and healing), which we can control, and external (other directed, futile), which relies on the other person to change, with helpful suggestions for exploring one's feelings and circumstances.   I thought it might be helpful to others, too, whether you're just starting out, navigating a MOM either willingly or not, or have divorced.