The other night the New York Yankees won the World Series, giving that team a grand total of 27 world championships. While my New York friends are elated, the majority of my friends back in Maine--Red Sock fans, every one--are bummed because the only thing they like better than seeing their own team win is seeing the Yankees lose. (Never mind that as New England "yankees" they are rooting against the team of that name. This rivalry goes back a long time)
Though a sports fan, I never really got into the raw emotions behind rooting for a team. I'd pick a team I liked--usually based on liking some players or coaches--and clap when they won, and if they lost, no big deal. I was never one of those people who could let it affect my mood in any real way. Some friends of mine suggested this was because I wasn't really a fan, or didn't "get" football/baseball (I don't count basketball since it's an annoying game to watch with the constant fouling and faking falling down and shoes squeaking. Hockey I like but find it hard to watch on TV. Soccer's fun but I don't get foreign sports channels). This is hogwash, of course--I find football and baseball quite enjoyable, both to play and to watch. But I'll agree that I don't have the emotional investment in a given team--part of this is due to the constant trading of players and coaches, and part of this is a detachment from those teams.
But I do understand those who get really into it--often it has more to do with a feeling of community with other fans--whether they're locals (Pirates fans, say, tend to have their Pittsburgh connections binding them) or there's a more personality-related reason (many non-New Englander Red Sock fans simply like the underdog, and that team had a notorious 86 year drought from World Series wins and some crushing near-wins). One friend of mine picked the teams he roots for based on his dad's favorite teams, and finds a connection with his father through this fandom. None of this really happened to me, as I wasn't raised in a sports-loving household, and upon leaving New York moved to DC where the teams suck so regularly that it's hard to develop an affinity to the players or rotten owners like Dan Snyder who totally sucks.