Hi there,
I've been in the situation you've described and I'm not going to lie - it's horrible. Having to say goodbye to him as often as I did (no more than any other services couple) broke me. I even cried when Rose said goodbye to Dr Who, that's what he did to me!
You have to focus on the coming back, that's one thing I learnt. At the end I started counting hours and they went quite quickly.
The other thing that helped me is the numbness. I had a guard that I would put up where feelings couldn't get me. It was horrible the first few weeks of the first couple of times, then it would only take a few days before the guard was up. Seriously, numbness.
Now I do sound like I was some awful mess, but I did get on with things, found myself saying yes to things that I wouldn't normally, just to have a bit of distraction. It's easy to become a hermit, so watch out for that.
You'll be ok, you really will. Write lots of letters (letters are nicer than eblueys, the handwriting appearing on their bed is a winner, apparently) say yes to your friends and count the days down.
Let me know if you want to chat while he's away. My reply hasn't detailed much of the feelings I felt, but if you don't want someone to moan to, let me know.
xxx