When learning any skill using memory, active recall is the mechanism which actually makes information useful. Let's say you read a chapter of a book, and you went through 5 key points. These points may be in your memory for any amount of time, varying in importance and impact. The goal is the create a strategy in your study plan that allows you to actively recall the points that you learned regardless of how it is in your memory. This is where testing keeps it knowledge, to not only retain the knowledge but create the necessary neural pathways to connect more concepts to each other and make it "useable". 

Re-reading information in the form of cramming is very ineffective in any field of discipline. This is because your brain is already aware of the information, but just not processing it. Instead of passively reading, you should actually attempt to use it. Things one has done are remembered far better than things done by others that one has observed.

If you are constantly practicing the same thing every single day, all your are doing is allowing it to stay in your memory. The best way to refine your knowledge is to switch up your practice and practice time. This also brings us to the different styles of practicing the content you have learned in terms of: Spaced Practice (Time), Mixed Practice (Difficulty), and Varied Practice (Concept Transferability). 

One of the best ways of understanding that we actually learning something of value is through the vision of Conceptualization. If we have a garden, facts are the seeds for the garden and concepts are the flowers that come from the seeds. When learning a difficult concept, you should be able to also know that knowledge is transferable among the concept.