I think the only way long distance relationships work is if you are both very independent and self contained, if you see each other fairly often (like almost every weekend), and you can see a light at the end of the tunnel when you can actually be together. Everything else puts the relationship on a clock until both parties drift apart, find someone else, or just wonder what's the point in being in a relationship where you're never together.
A lot of the time you feel in limbo or worse miserable because you're not with your loved one, and then when you are together it's all about manically spending time and doing things because you've got a couple of days of togetherness/happyness. The only way to cope when they are not there ends up learning to not care so much, learning to not want to be with the absent partner, not to feel alone or unhappy, and from there it's only a short step to deciding you don't need that person after all. Especially more so if you're meeting other people and getting attracted to them as per manic111. That person you meet starts to fill the empty emotional and physical space left by your absent partner.