Professional writers write. That's the biggie. They get up in the morning, check their pulse, and if there's a flutter, they stumble to the computer and tap the keyboard. Or they write three pages in their notebook.
You've heard it before: "writers write."
Just doing it - writing - is vital.
Follow your muse - it's not as dopey as it sounds
So here's the process professional writers follow that you don't: they follow their muse and trust the writing process. They know that words and inspiration arrive willy nilly - you can't manage your subconscious mind (your muse), but you can follow along, picking up the words and trusting that sooner or later they'll make sense and can be structured into some kind of order.
They also know that inspiration (your muse) arrives when you're writing, not when you're watching TV or are thinking about writing.
Amateur writers believe that the words they read in a book or magazine just magically fell onto the page that way. Professional writers fall about laughing at the very idea that that's possible.
Following your muse is the reason that writing more, and writing exercises, are so valuable.
If you don't write the crumbs your muse tosses you RIGHT NOW, this very moment, you've lost them forever. Writing happens in the moment: not tomorrow, and not "when I have more time."
Writing happens NOW. What you get when you write is what you get.
If you follow your muse, you'll get more than you believe possible. Write. Trust. Follow your muse. She/ he knows more than you do. :-)