This is a statement from someone who either hasn't been freelancing that long, or who hasn't realized that "brain down time" is just as important as raw coding hours. I've worked "for myself" for almost 20 years and for the first 5 I too panicked when daytime billable hours were derailed by "distractions". Once you push beyond that, you realize that those times away from your machine are valuable, and actually contribute to your overall well being, and your ability to code with a clear head, and an efficient mindset.
Wasting away "on salary" is a hard mindset to break. The answer is not to replace 100% of your salary hours with your own freelance work. You'll find even 50% of your previous salaried time can get just as much done, and make just as much money (assuming you price your services and value properly)