Fandom is a subculture that grows up around people who are passionate about a work when the rest of the world isn’t.
If the work is part of the dominant culture, nobody has to build a fandom around it. The Well-Tempered Clavier is assigned to every piano student—nobody has to organize clubs to listen to Bach in secret.
To have a fandom, a work doesn’t have to be bad. It can just be overlooked, forgotten, or left behind by the mainstream. Gilbert and Sullivan operas are pretty good, but they have a fandom made up of old-fashioned Anglophiles and intellectual showoffs. (I’m one of them, naturlich.)
It helps if there’s something totalizing about the work itself—if the author insists that it should change how you see everything about the world, then those who like it will make fandom part of their identity. (See: Wagner, Rand, Kerouac.)
I’ve learned a lot about the transience of moods by keeping track of them via Moodscope. I almost never have a similar mood two days in a row. Mood is weather, not climate. You are not one single person—different people pass through your brain, many times a day. Being aware of this hasn’t kept me from having bad moods, but it has made me stop believing in them, if that makes any sense. I don’t take them literally. I think “Oh, there’s that thought again. It feels true now, but it’ll feel false tomorrow, and true again next Wednesday.”
Being realistic about the brain means making your peace with flux.