UPDATE: Seesmic is now part of Hootsuite, which doesn’t support filtering based on excluding keywords. So during SXSW, I use Tweetdeck, which lets you filter a stream to exclude any tweet that includes a specific term.

If you’ve been using Facebook, Twitter, FourSquare or Google Reader for more than a couple of weeks, you’ve undoubtedly had the experience of reading about a party you weren’t invited to, a movie you haven’t seen or a conference you couldn’t attend. And since you’re an incredibly mature, enlightened person, you feel a warm sense of gratitude for living in an age where you can vicariously enjoy all of these other social and professional opportunities that you don’t have the knowledge, time, money or relationships to experience for yourself.

Or maybe you just occasionally feel the pain of FOMO: Fear of Missing Out. Because if there is one thing the Internet (and especially Twitter and Facebook) are good at, it’s letting us know about all the things we aren’t doing.

Conversely, it’s pretty terrible at letting us know about all the things other people aren’t doing. So when you read the 140-character tweet that says “Just had great chat with @worldfamousguru at #ExclusiveConference that will make me stronger, faster & more attractive to same/opposite sex,” what you’re not seeing are characters 141-180 that would have read: “….while my children cry themselves to sleep and my partner berates me for once again leaving town, work, home and family responsibilities.”

Going all Buddhist-y is one way to tame the FOMO pangs; writing in the imagined second half of a tweet can help, too. But sometimes things grow really desperate, like when you spot an online convergence of every single person you know, every single person you should know, and in fact, every single person on the entire planet who matters at all….except you.

In other words, SXSW.

SXSW is such a monolithic event in tech-land that for those five days in March, it can be absolutely excruciating to be online from anywhere other than Austin, Texas. Last year I coped with this dilemma through my preferred methodology: going myself. But this year, even my FOMO couldn’t get me out the door: my husband and I have back-to-back trips that will see one or the other of us out of town for 10 solid days in late March, and if I went to SXSW, it would be 15. That’s just too big a disruption for our kids, so I decided to put my family over FOMO (bumper sticker, anyone?).

As a result, I’m now suffering through an epic bout of WAIGTSXSWITIS: Why Aren’t I Going To SXSW-itis. It’s a temporary but painful seasonal condition that afflicts hundreds of thousands of nerds each year.

But now there is a cure.

Welcome to Seesmic Desktop, a Twitter client that has got some very nice features, including a “marketplace” that allows you to add a variety of enhancements. One of those enhancements is a Filter plugin that lets you automatically exclude any tweet containing a specific keyword.

Here’s how I’ll use it to get through the worst of my WAIGTSXSWITIS. While I will continue to use HootSuite as my primary client (can’t live without it!) I recognize that there will be moments (like, anytime I don’t have a drink in my hand) that I can’t deal with all the SXSW tweets. At that point I’ll switch over to Seesmic, where I’ve configured the Filter (under settings/plugins/Filter) to exclude any tweet containing SXSW, #SXSW or Austin (just to be safe — sorry, Texan pals).

Is this mature? Is this evolved? Is this the professional equivalent of sticking my fingers in my ears and yelling “I can’t hear you”? No, no and yes.

But so what? I am the same immature and emotionally stunted person that I was before Twitter was invented. All Twitter has done is turned up the volume on those insecurities.

If Seesmic helps me turn the volume back down for a few minutes — minutes when I may want to be actually present for another, non-neurotic engagement online — then I’ll happily embrace it.