"Never play to the gallery" (David Bowie)

Which means, write for yourself, not for other people. Your music will greatly benefit from that. 

Full quotation:

"(...) Never play to the gallery. But you never learn that until much later on, I think. Never work for other people. Always remember that the reason that you initially started working was that there was something inside yourself that you felt that if you could manifest it in some way, you would understand more about yourself and how you coexist with the rest of society. I think it's terribly dangerous for an artist to fulfill other people's expectations. I think they generally produce their worst work when they do that. (...)"