I must have tested close to one hundred students during my last four "days off," including a Friday.  The test was part of the English Bagrut requirements; that's the national high school matriculation exam.  There are three written tests and one interview.

The interview is based on a "project," a sort of research paper.  The students are supposed talke about their project for three minutes, and then I ask them questions for another minute or so.  One of my standard questions is:

What surprising thing did you learn about doing this project?

One of the answers surprised me.  The student did her project about the Rambam, who not only was a great Jewish scholar who "was the first person to write a systematic code of all Jewish law, the Mishneh Torah; he produced one of the great philosophic statements of Judaism, The Guide to the Perplexed; published a commentary on the entire Mishna."

The Rambam was a doctor, a "physician to the sultan of Egypt; wrote numerous books on medicine; and, in his "spare time," served as leader of Cairo's Jewish community."

The student answered:

"I was surprised that the great Rambam had a profession, a job. 

I thought that all of our scholars only learned Torah." 

The Rambam wasn't the only great Torah scholar in our thousands of years of history to have worked at a job or damanding profession.  Until very recently, it was the norm. There's no long history of full-time yeshiva students.  It's against the grain.  Judaism combines "Kodesh and Chol," the Holy and the Profane.  Every single job, from the "elite" of medicine to the simplest clerk or cleaner must not only know Halacha but understand it.  Halacha isn't "just theory."  To be a rabbi, posek, in the modern world, one must study and understand modern technology. To be a rabbi and posek, one must be part of the real world.

Research shows that when students take breaks, do other things, learn other subjects, during their studies, they learn and absorb more than if they just spend the whole day on one thing.