300 to add. 3000 to remove. It sounds like the Crazy Glue ratio.
Crazy Glue comes screaming out of the tube onto your fingers and then it takes 10x the effort to remove it. This is not about glue though, these particular numbers, or similar, have been floating around the sports training world relative to the number of repetitions it takes to form new habits.
I'm confused though. How is possible that it takes 300 reps to add a new habit and 3000 reps to break an old habit? Adding a new habit is simply telling your body to do something it hasn't been doing right?
The act of adding a new habit--by default--means you've replaced your old behavior with new behavior. By these numbers you should be able to do that with 300 reps. All of our subconscious movements are habits, and to layer a new on means over riding something even if we don't recognize it as a habit.
Spending 3000 reps 'breaking' a habit--depending on how you look at it--means you've acquired a new habit and practiced it 10x more than you needed to.
I think I prefer the Bruce Lee method. Deliberate practice of what you want to add without focusing on what you are trying to avoid.