"My sister said that she thought the reason that some friends have become less supportive to me, is their fear the same marriage difficulties could happen to them. "
Oftentimes it's because they feel awkward and don't want to take sides. It's not that they are less supportive of you, they just don't understand. Until it happens to them and the first person they'll go to for help is you because you've been there. You wouldn't believe how many of my friend's marriages I've saved in my personal life.
One of my dear friends (who actually married H and I) bravely admitted that her first reaction after I emailed her the news, after the shock and disbelief, was fear. She said she went home and asked her H "Are we okay?" I think it's a combination of the fear you mentioned and the lack of understanding as Bond suggested.
Bond, I would definitely believe the number of people you've helped in real life. Anytime I see you've responded to someone, I'm reading that post. You're a real DB Treasure (tm)
