Antonia - I think this is a tough one. I have two friends who are widows - one of the husbands was a close friend of mine. Both of them have told me that they think what happened to me was worse, in a way [I didn't ask for this btw!]
I think the betrayal is a huge additional factor, but the common area is that all of us feel at times as if we were 'robbed' of our future. What I also see in the case of MLCers is that some years down the line, they are still unhappy and confused. This is not my wanting to see it: my xh is a lonely and messed up man. So it does feel absolutely pointless.
I think what I was also trying to say is that a lot of stuff happens that we cannot see the point of, so all we can do is focus on recovery. What might have been and what we feel 'should' have been are huge drains on our recovery. I believe we have to go there, but not get stuck.
Another friend of mine remarrried about 10 years ago, and said she could not imagine every being so happy wit her first husband, who left her with two fairly young children. They had been together nearly twenty years when he left, and she recovered, met a lovely man some time down the line, and married him.
Like us she considered herself married for life. But she is now with someone else, and very happy. I have known her a long time.