When you’re trying to create a new habit, build a progression, develop a mastery, doing that thing for 10-20 minutes everyday for that week is much more valuable than doing it for 2, 4 or even 8 hours for just one day that week.
It’s about overcoming inertia and creating momentum. The secret is that 10-20 minutes will expand and grow into an hour, then even more hours. But they will be high quality, intentional, efficient, focused hours. So you won’t even need to go to 4 or 8 hours. You will be multi-hyper-focused, able to jump from one task to another, juggling different responsibilities, able to accomplish multiple things in a day, week, month, year.