Memory Helper

[What is Memory Helper?] Have you ever had such an experience that it's hard to recall knowledge when you want use it, even you have memorized it? Forgetting is an inevitable objective law, but letting it happen is a huge waste of your own efforts. Fortunately, review is the most effective way to fight forgetting. On the other hand, excessive review is also a waste of effort. For example, like constantly cleaning the ground which is already very clean. A lot of effort, but little effect. Me...