Most students spend a majority of their study time on four activities:
These activities involve no real commitment. Passive activities such as highlighting, reading, and copying have little long-term benefits, and trying the exercises before copying solutions is only minimally active. This kind of study leads to the common complaint, "I 'understood' everything, but I didn't do well on the test."
The words "doing" and "reflecting" imply activity on the part of the learner, rather than passivity.
"Doing" mathematics means reading and working problems actively.
Active reading and careful writing of exercise solutions takes a long time, but it is what teachers do when they prepare to teach a course for the first time, and it is a crucial learning activity.
We never really know that we understand something until we have successfully written it down or explained it to others. Often we think we understand an idea, but we find our written or spoken explanation inadequate. The search for a better way to say something can lead to a better understanding.