As explained above, the merit of Torah study is immense, as a person can amass tremendous wealth within minutes. How is it that people consider sitting idle for hours on end a matter of rote? Perhaps the reason is that in principle it is forbidden to write the Oral Torah, and in pre-Mishnaic times people had to memorize what they learned, otherwise they could not learn at all. When learning in the beis midrash they memorized the material, and at home and at work they would easily repeat what they memorized. When Rabbi Yehuda Hanasi learned from the verse, ‘[there are] times to do for Hashem contrary to His Torah’, that when the Torah is being forgotten one may write it down, he compiled the Mishna and allowed it to be written down. Perhaps since then people got used to learning only when books are available, and have trouble learning when not in a beis midrash. However, just as in business if a person sees a rare opportunity to become rich he jumps on it, so here he should make sure to have a sefer available to study in all his spare moments.
י״א בכסלו ה׳תש״פ
"והאמת בלתי שום ספק כלל, שאם היה העולם כולו מקצה עד קצהו פנוי חס ושלום אף רגע אחד ממש מהעסק והתבוננות שלנו בתורה, כרגע היו נחרבים כל העולמות, עליונים ותחתונים, והיו לאפס ותוהו חס ושלום". (נפש החיים) 1