Many years ago, I use to watch videos provided by Microsoft MSDN Network on software development. One day, I noticed a peculiar behavior. I would occasionally rewind the video by a minute or two. Once I became aware of that, I realized that I would often lose my concentration (and focus?) and so would not be in the present moment digesting the video. I then thought back to when I was still going to school and recall that the same behavior would occur during class. Unfortunately, in school, you can't rewind the instructor. I also began noticing that my mind would slip while reading. It also occurred many years later when I would listen to audio book and I find myself having to rewind the player.
Recently, I've become more aware that the most likely cause of my mind slipping is when it encounters concepts that are difficult to grasp. For example, when I read an answer to a post on this forum that is difficult to understand, my mind would wander and I would skim the text without really comprehending it. I would have to force myself later on to revisit the text again and again in an attempt to understand it.
I was wondering if anybody here have identified exercises that could be applied to improve concentration or if force is really the only way.
Also, is this an example of the mind losing concentration because it lost focus?