As I wrote in other articles, I am highly impulsive and hyperactive, though I am not diagnosed with ADHD. So much so that I have difficulty focusing my attention when studying. Fortunately, there are many books on concentration so I read a couple of them, written by doctors. In them, the authors said that since human beings can keep concentrated for 90 minutes at the longest, it is advisable to take a rest once in every 90 minutes.
So I made it a rule to study for 90 minutes and rest for some 10 minutes or so when I did research. But it was not long before it dawned on me that it was hard for me to remain seated and focused even for an hour.
Yesterday, I tried changing the rule: the new one was that I should study for 45 minutes and take a five-minute rest after each 45 minutes. It worked. Staying focused was a lot easier for me, and I felt it comfortable while applying myself to a book of philosophy. What the doctors say must be qualified, for I am not the average person who they base their research on and make conclusions from.