I dedicate this train of thought to the future generations of male "waiters".
I pity you. Obviously I have been in your shoes. If your girlfriend is on a mission now, you probably fall between the ages of 21-23, as I do. If, like me, you also live in Utah, all of your friends and buddies are married or getting married. You've probably realized that, now that your sister missionary is in the field, you suddenly have no friends. I'd like like to welcome you back to the Mormon Singles Club, you are now a social pariah. Soon you'll find out that you have to construct an entirely new friend base if you're going to survive and remain sane.
I don't know where the tradition of shedding all your single friends when you get married started. I can tell you that it will be the most difficult part of these 18 months. To be honest, there have been times where I've thought about hooking up with a rebound, and keeping her around, just so I can still hang out with my friends. These thoughts bring me back to the most ridiculous part of the Couples Club, your friends don't even have to like or accept your date, just as long as you have one you are welcomed.
I vow that, once married, I will have at the least semi-monthly gatherings with friends both single and spoken for. Yes it will be hard to resist the urge to dishing the same treatment to those of my friends who will inevitably get divorced, but I'll show some compassion, while still reminding them how they were totally douche-y towards me while they were married, which was probably a contributing factor to their divorce. Now I'm in no means saying that if you forsake all of your single friends once you get married that you're going to end up in a divorce; I'm saying that if you do end up in a divorce the fact that you could so easily forsake your less-fortunate, single friends was probably a largely contributing factor. It's called the pride cycle....