How Memory Works: 10 Things Most People Get Wrong — PsyBlog

#5 "Memory is unstable

The fact that the simple act of recall changes memory means that it is relatively unstable. But people tend to think that memory is relatively stable: we forget that we forgot and so we think we won't forget in the future what we now know.

What this means is that students, in particular, vastly underestimate how much effort will be required to commit material to memory. And they're not the only ones."