Do the job before you have it
Your goal is not to publish a book, but to be a writer. You can be a writer today. I'm being a writer right now. This is what writing is like, and it wouldn't be much different if I was a famous author.
Because Systems are better than goals and You'll never get there, writing doesn't magically become amazingly fun just because now you're a "writer". You can see how much you like whatever you want to do right now, by just doing it.
No, you can't see what it's like to be rich and famous right now, but it wouldn't be worth it if you didn't enjoy what you want to do to get rich and famous anyway. (It's also probably mostly the same as regular life).
References:
You might get bigger faster and make millions if you outsourced everything to the experts. But what's the point of getting bigger and making millions? To be happy, right? In the end, it's about what you want to be, not what you want to have.