No, you aren’t writing for yourself says Vonnegut.

Hear hear!

I found myself just yesterday trying to very gently criticize a writer who had produced what felt to me like a largely incoherent mess.

They had clearly had great fun writing it. It clearly resonated strongly with them. They loved it.

I couldn't figure out what the hell it meant, and I figured that the average reader would feel the same way. It was "self indulgent," a description many of us fear from an editor or a critic.

Self indulgence is the flip side of the writing-for-yourself advice. As you say, it's perfectly acceptable for a journal. It might be okay if you're Kurt Vonnegut or David Foster Wallace, or some other luminary whose books professionals will sweat over. (Calm down, everyone. I've quite enjoyed books by both those authors.)

Otherwise, I think the idea that you're writing for other people, to share something with them, even to expose your soul to them, needs to be a focus.

Art exists in a mystical space between the artist and the consumer. That goes as much for writing as it does for any other form of art.

And I learned that from John Simon. He writes okay sometimes. ;-)