Vise, I struggle the same way you do. But I have put my faith in the process as well. I think there is a point in time where NOT DBing is the right thing to do, and to shower her with the "new you" changes you are making in your life. But once things reach a certain point, that "cherishing" and "compassion" you show for her, just does not have the same affect it once did. Once, in her mind, she's filled her image of what you are as NOT a H, and instead, the father of her kids, or 'friend' who is having to suffer through the same hard things she's suffering through in life, these thing just don't work, and that's when the DB-process seems to be the only way back.
I didn't understand it, and still don't fully understand it. When W says things like "I want to believe you, but I just don't think things will ever change," or "I know you're capable of anything, but what makes this any different than the last times we tried to work things out." I personally feel like she's fishing for me to jump all over the bait, with reasons, examples, analogies on WHY this time it's different, and this time I'm REALLY going to be the better man she's always dreamed of in a H. But, it's too little, too late, as so often said.
What's helped me understand this a little bit better, isn't something I learned through DB, but through psychology resources on why a straying spouse is so unlikely to give in to these things. And it's because they fear that nothing is ever really going to change if we save THIS RELATIONSHIP. And a better way to look at it for me, has been to look at it through the lenses of... "I don't want to save this relationship, I don't want to save this marriage, I don't want to stay in a marriage with these same two people who want to make changes." Instead, "I want to end this MR, and start a NEW MR, a new M and a new Plan for life. This is very common in cases where there is an A. The ones that overcome these obsticles rarely will tell people they 'saved their MR', but that they started a new MR with the same person, just with a different outlook and a different stance on life.
I think the key to created this view of "end MR, start NEW MR with same person, is to kill off ALL emotional ties, all psychological ties, and sexual ties, etc, with the old spouse in the struggling MR, and the only way to do that is to follow this process of detachment, and eventually re-attachment, to that new person. People don't change over night, and there is no way your S is going to think that just because you're saying XYZ, she's going to believe it. She will be forever, watching, waiting, judging, waiting for you to slip up and then boom, SEE! I told you you weren't going to change! The distance and detachment is necessary in order to get those habits of your S to no longer be associated with the past issues of the MR.
