Masello's first rule of writing is one that I'm sure will generate a lot of controversy, so in a way, it's an excellent place to start.
Masello dismisses the advice he has found in many other writing books, which say that if you're stuck on something, or don't know what to write, you should start keeping a random journal. He feels that this is "a way to tell yourself that you're working when you're not." His suggestion is that if you want to write something that someone might buy and publish, you need to skip the journaling in favor of the "grunt work that real writing requires."
Now, on the one hand, I think he's being a little harsh. Most writing books I've read suggest journals for specific reasons, such as developing a character's voice or keeping a book of ideas for stories. There's also other types of journaling; for many years, I kept a paper diary, a record of my life, and I now do the same thing electronically.
On the other hand, though, it's not hard to see where he's coming from. I'm guessing that in his years of teaching, Masello has met a lot of people who want to be professional writers and who spend their time scribbling down pages and pages of reflections but never once concentrate on the type of writing that will help them achieve their goals.
So as much as I hate to say it, he's right. Keeping a private journal doesn't get you published. And keeping a public journal, such as this blog, does have the benefit of keeping you in touch with your readers, but it's not going to be your primary source of income. (If it were, I'd know, as I'd have more people going to my home page and clicking my PayPal donations button.)
In short, if you want to be a writer who gets paid for what you do, a writer who makes a living, you need to focus your writing in that direction. And that might very well mean abandoning the journal, or at least relegating it to a smaller portion of your writing life. Because every minute you're writing in a journal, you're not writing pay copy. Which, if you want to be a professional writer, has to be your final goal.