Writing is a discipline, it is a habit which can’t be easily established. A way to inculcate a healthy writing habit is to write every day. Yes, every single day.
If you are one of those who say I write once a week for 6-7 hours; then I am sorry to say that doesn’t qualify as writing. Your focus will be off after a week of not writing, also the progress will be negligible. Your speed too will be as slow as last time, soon you will find yourself quitting.
A good writing habit is that of writing every day, even if it is for 30 minutes. It is safe to assume, anyone can manage 30 minutes of writing. Key is to be focused on your goals, no matter how short, just keep at it. This helps you to keep better track of the trail of thoughts from where you left last day. A daily habit establishes a pattern that makes the writing easier, in a short period of time.
If you write often you fail often, you get used to failing and failure suddenly stops affecting you anymore.
If you want to turn pro, make writing a daily habit.
Serious writers write inspired or not. Over time they discover that routine is a better friend than inspiration.