I was in your position this time last year with DD1 and I absolutely promise you it will get better. 
The day I drove her up to her new flat in London (70 miles) I will never forget. I'm a real country bumpkin and I hated the whole area, couldn't bear leaving her there, but in the end just kind of abandoned her there even though the other girls she was sharing with (who she hadn't met) were out. She was looking so plaintive and saying "do you have to go yet?" And I just said "yes, no point me hanging around" as I was just so close to losing it entirely. Then I drove to Bluewater which is more or less en route back and stopped there as I couldn't face going home without her. I walked round until they closed, just numb. I felt like I'd just been through the worst break up in the world. All I could think of was the times when she was two years old and with me all the time and that all that was over.
The first term was hard. I hated my job all of a sudden - really hated and resented every minute of it, and was ratty with DH and took it out badly on DD2. Looking back I really was pretty depressed and it might have been an idea to start some antidepressants in retrospect. DD1 was terribly homesick too and was apparently crying a lot in the evenings. Yet she stayed away and so did I because I think we both felt she should be grown up and independent. Two weeks in, after both crying over FaceTime I said, I'll come up for the day on Sunday. Seeing her again was just the best thing ever.
After that we both kind of realised we weren't so far away and it didn't seem so bad. It's 2-3 hours to get to her, but for many weeks I went up on a Sunday morning and spent Sundays there with her. I came in for quite a lot of stick from friends for being too clingy but it was a mutual thing - DD was desperate to see me too. DH was infinitely patient with me over it all, which helped.
She came home for Christmas, which was lovely but surprising how much extra work it created! When she went back it was much better. She'd made friends and much more of a social life and was busier at weekends, and I'd started using the time to do more with DH as catch up with old friends of my own. By the Easter term I didn't see her at all except for half term. We were both busy with our own stuff. We kept in chatty touch over FaceTime a couple of times a week, but the term suddenly seemed to tick along really easily without me needing to count the days and weeks.
She says she will stay in London after the course and I'm amazed at how cool I am with that - she needs her own life and I can see that it's better for her - vibrant, happening - than being stuck here in the sticks. She's at home now for the summer which has been lovely and hard work in equal measure and I know I will be 100% fine when she goes back.
Sorry that was long but I just wanted to say you could barely be more pathetic than I was and a year on it is all absolutely fine. I enjoy hearing all about her life, and I really enjoy having time just for me and DH to do stuff just for ourselves.
I'd say focus on every other thing you possibly can, work, your DH, other friends, and fill your life as chock full with socialising and hobbies as you possibly can. Visit as often as you both need to start with because you won't need to do it forever. And know that you will cope. If I can, anyone can!