Not ALL long-distance relationships need to be miserable!

Yeah, people do get more needy with distance (I definitely do), but every relationship has its ups and downs, no matter how geographically close or far apart the people involved. So it's just about learning to deal with the circumstances as best you can.
I guess it depends on #1 how in love you are, #2 how much you love each other and are committed to putting the work in (e.g. making up for physical closeness with even greater emotional closeness/sharing), #3 how long the separation will be, and #4 how far apart you will be.
I'm right in the middle of learning to deal with a long-term, mid-distance (3 hours' drive) relationship. I know that I couldn't have dealt with a super-long-distance deal (as in, different countries for possibly months in between)... but I think that if you are with the right person, you will find ways to manage that distance. We're working on it, though that doesn't mean easy answers for everything.