Epiphany: the comprehension of the meaning of something through a sudden intuitive realization.
Had one just the other day.
It's strange. You read something and go "yeah, that's good." And you acknowledge that it's something that you "should" do, but you don't.
And then, some time later, you're discussing it with someone else, thinking about it in the shower or the realization just pops into your head from your subconscious. And you just suddenly get it. A total and utter understanding of WHY you should do it.