I didn't know what I was doing to my W either. I never would have knowingly continued behavior that caused her so much pain, but I didn't come up with this. It's what I learned from reading, Gray, MWD, and Patricia Love, among others.
I certainly don't suggest facilitating the divorce, but they know how difficult and painful it is. Bear in mind that they have come to the point of choosing the lesser of two evils (divorce being the lesser of the evils!) and they do whatever they need to do to rationalize it. Make THAT difficult for them. Start by making the R the less painful choice and you might get a chance to make the R not just less painful, but fulfilling.
Don't fawn. Don't play the martyr. Be compassionate, but don't let yourself get walked on. They didn't make this decision because they wanted us to be doormats. They made this decision because we did not provide the kind of R they wanted. The common element is usually lack of validation, but lack of engagement and other behaviors that you need to identify and change usually come into play. I was able to figure out most of it by myself. For instance, I withdrew into myself to deal with my stress. The validation thing I never would have figured out by myself without research. (It's just a foreign concept to us and seems to be completely illogical, right?)
How do you start validating? Baby steps. Validating doesn't mean agreeing. It means being empathetic. Ask her how her day was, or if anything interesting happened and listen. Don't make suggestions as to how they could have done something differently. If they complain about something, agree that it stinks, or is unfair, or insulting, or whatever they think it is. This is not patronizing. I have learned that my wife longs to talk about her day and tell me about what happened and her frustrations. She needs this. I try to provide it. I began to realize that most of the last few years we usually talked about me, not her. I also realized that she is really funny, intelligent, and quirky and that's why I fell in love with her in the first place. And, she has F'ing amazing eyes. How's that for a revelation? I think I've looked in her eyes more in the last three months than in the last three years.
BTW, once you learn to validate, you tend to do it all the time. I was a grief coward. Couldn't deal with people who are grieving. Why? I figured out that it frustrated me that I couldn't fix their grief. When my neighbor's mother died recently it suddenly occurred to me that I don't have to make her feel better. All she wants is empathy. So, instead of avoiding the subject I asked her how she was doing. She began to talk, I began to empathize. She felt better and so did I. She got to talk and get some empathy and I was off the hook for making her hurt go away.
Anyway, I don't know what will definitely work in any given situation, but I do think it's important to understand what really happened. We stopped nurturing the relationship (maybe they did too, it's not all our fault) and it crushed them. And that explains why they did this. Deep down they don't think WE love THEM.
