I've been a professional writer for 30+ years. A friend just starting out to be an author asked how I ever managed to finish a book, with all the distractions: here's what I told him.

"You have to have a place to write, you have to have a schedule, you have to shut the door, you have to become a bear about interruptions. Everyone must learn to respect that daddy is a writer, and when daddy is in his writing den, others disturb on pain of injury! This is the first step.

Get anal about being in your room for your period of time every day.

And, in your writing time: never answer the phone, have your wife take messages or let them pick up. AND stay off the internet during that time! It will eat your life.

Also this - I learned it from Stephen J Cannell many years ago: never again start a story/novel that you do not finish...even if you know it's going to turn out badly. This will turn you from an amateur into a professional!