The idea that one should fake it until one makes it is rather odd (and poor) advice. What value is there in being a fake, a phony? More still, how does faking it lead to making it (whatever that means)! Dressing up in the clothes, buying all the gear, and posing does not make you that thing. Instead, it makes you a poseur.
Instead of pretending to be something you’re not, become that thing that you want to be. Follow the advice of Emerson, recognizing that we become what we think about most of the time. Nightingale shortened this to “We become what we think about.” Period. And it’s true.
The vision of what you want to become is the starting point. You must see clearly what you want to become. Then you must begin doing the work to become it. Don’t pretend to be something; actually, become it by taking the actions that all of those who came before you took in becoming whatever it is you aspire to.
You are better off being a bad version of whatever you are trying to be than you are faking it. If you paint, you are a painter, even if not a very good one. The tools of the painter don’t make you a painter, only painting does. If you want to be a writer, then write. You won’t be faking anything because you will be a writer simply through the act itself. You will have written. Every master started out as an amateur, and their work was no less embarrassingly bad than yours.
The making it part is more difficult. In some endeavors, one’s mastery is no guarantee of success (at least as it is defined by some). That is in larger part determined by will and perseverance. But if success is defined as mastery, working on becoming what you want to become is almost guaranteed.