Originally Posted By: Zen Scanner

We learn best at our level challenge, when ideas come in and connect with things and we work a bit to make sense of it. When the information is engaging and interesting, we put more focus and more of our mind on it at the time; the boost of the thrill of succeeding also makes the recall better. If you're floating in a bored zone, your brain engages less and encodes more shallowly; active attention is the currency of memory.

This is very well put.