Are you familiar with the "forgetting curve"? I was about 16 when I came across it, printed in the back of my physics textbook at secondary school. But I have a vivid memory of that discovery to this day. The graph had a tremendous impact on the way I approach learning, especially when studying Japanese.
Our brains organize and process information in order to recall the most important stuff first. I’m sure most people can relate to the frustrating feeling of having studied a new and tricky word, only to find it has ceased to exist inside our head the very next day. "What happened? Surely I’m not getting old already?" we fret. Perhaps we should blame a bad learning technique instead of our memories.
Age, stress and sleep — among other things — all affect how well we remember something. Typically, however, one of the biggest problems is that we aren’t even giving our bodies a decent chance to recall things in the first place. With the constant flood of information entering through our senses every second of every day, our brains have quite a job to sort out what is important from what is forgettable.