I've come to an understanding of why long-distance relationships suck. Communication can be infrequent, and the result is that nagging doubts about the strength of the relationship ("Maybe she's seeing someone else over there? Maybe she doesn't want
to talk to me?") have more time to gestate and make themselves heard. Fighting those away depends on how secure a person you are and how much you trust your partner. If you aren't strong enough for it, the entire thing falls apart in your head, while your partner is blissfully unaware... you can even make things worse by making 'last-ditch attempts to save what we have' by attempting to contact them through every means available to you, and you come off as clingy and paranoid. (Not least because you're being it).
Of course, I'm not in a long-distance relationship. Because they suck.
However, it does give me a vague idea for a two-player cooperative game where you have to defend your Relationship from small, imp-like Doubts by smashing them with your head.