I don't recall the specific wording, but the best piece of advice for me was something like this:

Don't try to be a writer. Don't try to be an author. Just write.

Having an ideal identity which I was constantly and very unfairly measuring myself against prevented me from writing anything at all because before I even got started I knew it wasn't going to be to the standards of my imaginary avatar. I now allow myself to write a mess because in that mess is some quality stuff which I can extract and expand on, and writing the mess is a lot of fun. I'm currently totally free of an audience I have to conform to, so my writing is totally free from any kind of restrictions other than what I prefer at the moment.