I remember a song in the 90s with those words, or something similar. Somehow it was the first thing that jumped to my mind when I thought about why I had to leave my current guild.
Sometimes people leave their guild because they don't love it, or they don't fit in somehow. Last night I left Phalanx on my main, Solidfaith. I did this together with 4 other people, not because we don't love Phalanx, but because raiding had completely stopped lately and there was no solution in sight.
In hindsight, perhaps it should have been obvious. A 10 man serious raiding guild is a strange beast, caught in the middle, not good enough for the serious raiders who want 25man loot and achievements and the casuals who only want/are able to play once or twice per week, who cba to read boss tactics or show up for raids prepared and on time.
So, as much as we (the Phalanx officers) tried, we just couldn't recruit serious raiders. And the casuals who sometimes joined us claiming to want to raid but then barely showing up to raids just made things worse. As we lost raiders due to attrition and RL reasons, we simply didn't manage to replace them.
Some people might think that us leaving Phalanx is just another variation on the raider who has geared up enough in his current raiding guild and jumps to the next higher level. But there is a big difference between leaving a guild still actively raiding and leaving one which doesn't even manage to have enough people online to raid, night after night.
My new guild has at least 3 people I know previously (have guilded with), apart of course from the people I moved-in with from Phalanx. There are also several people I have pugged with who I know to be good people. So I felt comfortable right from the start, not a "stranger in a strange land".
In addition, right after we joined last night we were invited to a 2nd 10-man Ulduar run (the guild does 25man raids during the week and 10man during the weekend). Even though we were new and this was the "b-group" we still managed very nicely, taking down FL, XT, Kologarn, Auriaya, Hodir, Thorim and Freya. Not exactly the order I am used to but still half of Ulduar cleared after a late start and with people not used to playing with each other? Not bad :)
In addition, even though I am new and have no DKP I still was allowed to win (by roll) several items of gear - I won new shoulders and a new 1-h weapon (dagger) which are a very nice upgrade to my gear.
So long Phalanx, it's been a long road, not easy but with a lot of satisfaction. We did very well for a non-hardcore guild IMHO, and I have nothing but respect for all the great people who made it happen, including those who due to RL could not show up for every raid. I'm sorry it didn't work out better but I think those left behind understand.