There is only one single rule that it seems every writer absolutely has to follow. To be a writer, you must write.
No matter how talented you were in your high school creative writing class, no matter how specular the praise was from your letter to the editor was, and no matter how hard to dream of writing a book, you can't write unless you write.
Give it time
Writing doesn't take a whole lot of time. You can sit down a punch out a few hundred words in fifteen minutes. They might not be good, but "the worst thing you write is better than the best thing you didn’t write." No one knows who said that, or when, but whoever it was had the right idea.
If you are short on minutes during the day, don't sweat. Just form a habit. For ten minutes before bed or when you wake up, or while your coffee is brewing or while the kids nap, sit in a spot where this is nothing for you to do except write. Set an alarm. Then write. Once the habit takes hold, you'll be putting in 200-1000 words in those ten minutes. 200 words a day times 365 days in a year is 73,000 words. That's almost a novel right there.
Don't get discouraged!