Been in the same situation decades ago. Turned out she was chatting with a dude online (it was that time when ICQ was hot), out of the blue she decided to end our relation and move overseas to live with that guy. I went through all the 5 stages of grief.
It wasn't easy, but I had friends (with rotation I sleep at their places). When alone, I watched alot of funny stuff on TV. One day I received a call when I was cleaning my place, it was a friend I knew since I was little. We clicked somehow, 6 months later I was married and decided to move overseas.
My ex is divorced 2 times now, under plenty anti-depression pills. Sometimes you don't have to jump of a cliff to verify if it's deadly or not. Never leave a healthy relationship thinking there is something better out there. Of course there is always something better, but it doesn't mean you fit in.
So it will take time, but this is not end. It's a new beginning, just like learning again how to crawl, walk, then run when we were babies...
Good food for thought. There IS something better, but doesn't mean you should go looking if what you have is great. I mean there's a fine balance between always striving to do better in anything In life and actually being content with what you have.