Effortful Recall (II):

"Effortful recall of learning, as happens in spaced practice, requires that you "reload" or reconstruct the components of the skill or material anew from long-term memory rather than mindlessly repeating them from short-term memory."

...

"Massed practice gives us the warm sensation of mastery because we're looping information through short-term memory without having to reconstruct the learning from long-term memory. But just as with rereading as a study strategy, the fluency gained through massed practice is transitory, and our sense of mastery illusory. It's the effortful process of reconstructing the knowledge that triggers reconsolidation and deeper learning."

make it stick - Brown, Roediger, McDaniel