It is this vulnerability before the social lash that makes being left out so bitter. Yes, you are missing the party, but that is usually the least of your losses. What cuts is that you have been wounded and your friends stand by observing the assault, discussing what you might have done to provoke it. Even if they agree that you were innocent, they are unlikely to defend you. It is, they imply, not their business and, most of all, not their problem. It is, after all, only a pajama party.
Perfectly, indisputably true—which is why neither you nor I would press a friend to intervene in so small a matter. Yet this absence of loyalty was so unattractive that good friends felt compelled to explain to me why they had chosen it, citing social obligations, marital conflict, or business relationships as their reasons for participating with a smile. I outwardly agreed with their decisions, all the while feeling callously abandoned.
Exclusion hurts so much because it forces us to face the firm boundaries of self-interest that lurk beneath the surface of even the warmest friendship. If home is where, when you go there, "they have to take you in," then friendship is where, when you can't go there, your friend might cheerfully go without you. That realization of being excluded can leave scars—but they don't have to be permanent.
It's best they not be because inclusion and exclusion, sharing attention with others in your social circle, and respecting boundaries are issues in the strongest friendships. Part of what some people experience as exclusion is really only the normal balancing of attention that multiple friendships require. Extremely sensitive (or especially controlling) people, who suffer whenever they are not a part of every party, hold their friends hostage to their hurt feelings. ("We have to ask Jane to lunch, too. You know how she'll carry on if she hears about it.") In the long run, though, these demanding souls cost themselves friendships.
By adulthood, most of us develop a fairly high tolerance for sharing the affection and attention of our friends. We only feel left out when we are excluded in a pointed way. And even that sharp psychic jab does not have to cause permanent damage to your friendship network, though it certainly can test it for a time.
Exclusion is a part of life in any group. Human beings are pack animals, and it is in the nature of the pack to create cohesiveness by establishing a common enemy. That's why countries pull together during wartime and why little girls spend so many hours at a sleepover ripping apart the classmate who didn't get invited. In the politics of my friendship group, it was simply my turn.
I also considered the fact that, over the course of a lifetime, it has been my turn to be temporarily banished more than once, while some people never seem to sit one out. Groups may tend to draw closer together by excluding someone, but some of us are more likely than others to be chosen as that someone. I needed to consider my part in creating my sporadic social exile.
It didn't take much reflection. The thing is, if you're looking for someone who occasionally offends, well, that would be me. I can get an I-refuse-to-look-the-other-way smugness that has sometimes caused those who exercise social power to kick me right back—maybe even deservedly so. It's possible I did wince too openly in the presence of my friend's angry marriage. I broke the very common agreement among friends to never publicly react to someone else's marriage.