My opinion? I think it's a matter of coming to grips with it all.
I had a girlfriend back home. And I know, deep down, I might be stuck here forever. And I don't think it'd be cheating if I dated someone here.
The problem is, I'm not READY. I'm still so hung up on Julie... I can't even tolerate the thought of being with someone else. I think as long as you can "deal with" your loss... there's nothing wrong with trying to move on.