This has happened to me as well. I have lost many friends due to depression and anxiety. But I think I'm finally realizing that it wasn't just my fault that these things happened. Friendship is a two-way street.
I found out my friend got engaged via facebook. We've been friends since freshman year of high school and we're in our late 20s. So... we've been friends for a long time. The last time we spoke she told me that she was frustrated having to hear about my depression all the time. Mind you, I did the same for her before she met her now fiance. I'm trying to just let things go now. I feel sad but I definitely miss her. She was my best friend and the closest thing I had to a sister. It's been almost a year now since we've spoken.
I told my grandma all of this recently and she told me to think of her warmly, and to send her good thoughts. She's pretty smart; it's helping I think. Maybe you can try the same thing. Sending warm thoughts to all of you.
Sorry for the long post!