Careline, I know how you feel
My fiancee and I separated a short time ago, and it was the most devestating thing I've been through (emotionally). However, our situation was a little different because (I found this out later), he felt the same way I did. It's strange that we agreed to part peacefully, but came back together because of our grief...
but, getting back to my side of it:
I tried being with someone else, I tried pursuing others unsuccessfully, I tried all kinds of things. It was a time of strange, horrible confusion. I didn't know what I wanted anymore, because "the ideal person" I'd always wanted had entered my life and was gone. I didn't know who else I could be happy with. I'd even said before when we first got together (how funny, that it ended up being true) "If this fails I don't know what I'll do, because you are perfect for me..."
Luckily for me, he was just as distressed as I was, and after a strange silence and a lot of sadness we fixed the mess.
I definitely can't guarantee that your situation will have a happy ending, and for that you have my condolences. I have indeed felt the "I lost my "one" person..." pain before, and for your sake, if this doesn't repair itself I hope your instincts were wrong in guiding you that way
HOWEVER, if worst comes to worst, yes you can heal. Imagine what you'd do if he'd died, instead. Deal with it the same way if you must... This wonderful person was amazing, but now they are gone. Sometimes even our soulmates must leave us, somehow people can heal over time.
Best of luck to you

(PS: Have you spoken with him about how you feel?)