I can really only relate to this as the husband. My wife had ALS so she never recovered but I can remember years of feeling like I’d lost the woman I’d married. I didn’t step outside of our marriage but I can imagine if she had lived for many more years how difficult it would have become to remain faithful in the face of such trying circumstances. Then again I can easily see your point of view also. I am a believer in promises. I like to think I would have been completely understanding and willing to work with whatever came up but I still wonder. Would I have been that man? I hope so, but I’ll never know for sure.