Spaced repetition is a system of learning that has been proven to improve the rate at which people learn. The system entails repeating lessons that have been learnt in the past. Those lessons which are well know are repeated less frequently, while those that are not well known are repeated more frequently.
In your course of learning, it is good to take a break, or create space to review past learning. Purposefully include rest/review days as a part of your learning process.
When I heard about this technique, I started applying it to myself and my children and so far it is proving to be effective. You can actually see a mirror of this principle applied in the gym, and it works for those who are improving their fitness.