Contrary to what you think, you probably do not remember things as accurately as you think. A study done in 1988 by Ulric Neisser proved that many of our memories change overtime and become somewhat inaccurate. Neisser handed out a survey to some of his students following the Space Shuttle Challenger explosion. He asked them where they were when they heard, who they were with, and what they were doing. Neisser followed up two years later asking the students the same questions. He ranked their accuracy on a scale of 7. On average, students got less than 3 with 25 percent receiving a zero.
Scientists think memory begins with encoding. The memory is then consolidated until reaching the final step remembering or retrieving the memory. Each and every time you remember something, the neural pathway to that memory gets stronger. This could be why the students were inaccurate in remembering where they were or who they were with. I would assume that the students did not access those memories frequently so, the neural pathway to those memories was not strong.
This could be why many studies have shown it is better to study for 2 to 3 hours and then take a break instead of cramming for 8 hours. The more times you revisit the learned information the stronger the neural pathway. This makes the memory easier to retrieve come test time. If you are just cramming the information over and over again you are not allowing the information to go through the cycle of formation. When you access that information so quickly after introduction, you are not fully retrieving it.
In all, I found this video most helpful in beginning to understand the complexities of memory.