And it is supposed to be 10,000 hours of "deliberate practice", if I remember correctly, i.e. exercises and trials focusing on harder point, with an immediate f

And it is supposed to be 10,000 hours of "deliberate practice", if I remember correctly, i.e. exercises and trials focusing on harder point, with an immediate feedback. I don't think it is possible to keep that kind of focus 9 hours a day for 3 years in a row.