The Art of Study is Not a Voluntary Gulag

Because it's unnatural.

Why would you even want to..?

What are you, Asian..?

...'cause if you don't practice, then you might as well give The Clarinet to a kid who'll use it.

Kim's mother called me just after he left her. 

Delightful woman. He's her only son. 

He'd left his clarinet behind. 

She wanted to know if she had time to send it. 

I had to tell her no. 

I think (1) you can't do it and (2) you shouldn't try. No one can actually study that much. It is very rare for people to be able to concentrate  hard for more than three hours a day.

However, if you absolutely must....

1. Don't study more than 7.5 hours a day. You will just wear yourself out. More won't help. You can't learn when you are exhausted.
2. Take a day off per week. Do something you like on that day. You are in this for the long haul, so you can't wear yourself out. That would be counter-productive. Your job is to learn, not to prematurely die trying.
3. Make a plan. What knowledge is most critical in each of the subjects? First, concentrate only on that. Imagine that you are first planning to obtain the easiest 50% in each study area.
4. Study from low to high resolution. Familiarize yourself with the central ideas of the study areas. Then, and only then, concentrate on the details. This means that you have to broadly outline the study domain, as if you were summarizing it in essay format. I have produced a guide to such an outlining process here: http://jordanbpeterson.com/Psy43...
5. Nap. A lot. Study for 2.5 hours. Take a break. Eat something. Do something mindless, like watching a Simpson's episode. Then have a nap. That will refresh you, and also increase the probability that you will remember what you have studied. Sleeping helps consolidate memory.
6. Study one topic for 2.5 hours. Then switch to another. Continue.
7. Read. Then put down the book. Then summarize what you have read. Don't look at what you were reading when you summarize. You have to practice recall, not repeatedly expose yourself to the same material. You are practicing remembering. That's what makes you good at remembering. Going over the material ad nauseum won't work. It just feels like work, without any of the actual difficulty of work (or the benefits). Don't highlight or underline or anything useless and self-deceptive like that.