This randomly popped up as I scrolled so figured I´ll reply even though the thread is a bit old.
I can see where you're coming from, I feel exactly the same sometimes. We're not that far apart in terms of travel time but we're both really busy with work and commitments outside, so practically it's LD.
Like you say, the hardest are times like Xmas/ other big holidays, or being sick or in hospital alone, or him dealing with something tough and me feeling useless not being able to give him a cuddle and kiss it better.
Have found that developing a routine works, e.g. talking to each other at predicatble times, such as breakfast, lunchtime and evening. Also, planning the next time when you see each other, and talking about the things you look forward to when you're together next seems to help, as it's sort of a 'light at the end of the tunnel' effect. My bf gets me little presents that are things that I can see on a daily basis, such as a houseplant or favourite coffee mug, keyring... Seeing those simple everyday items daily somehow make him feel part of my routine.
Overall, try to build security and reliability within the relationship, so that you don't feel anxious when he can't be there or start questioning if they care (unless there's objective reason to of course!).
In terms of positive outcomes, we've ended up arranging our schedules so that we can see each other a little bit more and that's really lovely and going in the right direction. I've also learned how to deal with missing him a little better and yes, telling him if I'm having a rough day and would love nothing more than a cuddle, but also taking a step back and thinking through what I'm really feeling and why, and what I can do about it right now myself.
He probably feels very similar but generalising, men can be a little less expressive around these things.