Practice is important for building skills, and for knowing the piece.
The point is that you should be able to play the piece like you know how to walk.
Imagine: if you had do 'think' about walking, about every step, you would walk unnaturally. You'd certainly not be able to swatter.
When you can play as you walk - then - you can loosen up, and focus on having fun, making it creative i.e. have swagger. The actual notes are mundane, like walking, then the music can come out. If you have to think about it, it needs more practice.
Also - 'work' is not 'music'. Most of work is not practice, it's building stuff.
A carpenter who worked 1/2 days would probably get just about only 1/2 done, for example. I know tech is not quite the same, but it's mostly similar. We are not solving complex math problems, most of tech is mundane.
A programmer can usually average ~4 hours of focused highly productive work where they are not on Hacker News etc per day. Fewer people can do that kind of focused effort for ~8 hours a day regularly. I have never met someone that can do that kind of highly focused effort for ~12 hour days.
That does not mean highly focused effort is the only valid type of work. But, it is very valuable for most programming jobs.
Further, cutting back hours often increases productivity even if you spend the same amount of time in the office.
Modern day programming is so much more than just opening up your IDE and churning out code. You have to collaborate, talk, review other people's work etc. There is also a meta aspect to it to improve you productivity at work by looking at your own work from a level above.
You also have to keep learning new bleeding edge stuff to not be out of business in a few years.
Plus doing a lot of side projects and extra work, always opens up avenues for new opportunities and helps you to meet with other smart people who often have something new for you.
All of this is work. And there is no way you can be good at this if you only work for 4 hrs a day.
Practice is important for building skills, and for knowing the piece.
The point is that you should be able to play the piece like you know how to walk.
Imagine: if you had do 'think' about walking, about every step, you would walk unnaturally. You'd certainly not be able to swatter.
When you can play as you walk - then - you can loosen up, and focus on having fun, making it creative i.e. have swagger. The actual notes are mundane, like walking, then the music can come out. If you have to think about it, it needs more practice.
Also - 'work' is not 'music'. Most of work is not practice, it's building stuff.
A carpenter who worked 1/2 days would probably get just about only 1/2 done, for example. I know tech is not quite the same, but it's mostly similar. We are not solving complex math problems, most of tech is mundane.