Yeah, I breezed through school too but it caught up with me toward the end of high school. All through grade school and my first couple years of high school, I'd been given the impression that I didn't need to study or work at all to pull all B's and a couple of A's. So when I got to classes like AP English where I had to work hard, I did fine, because writing essays was fun for me. But when I got to classes like Trig and AP Bio and Chem, I suffered, because I simply wasn't willing to put the amount of work into them that they required. I, honestly, didn't know how to. I remember everyone in my AP Bio class freaking out for an exam that I hadn't even studied for... I guess at that point in my life, I simply thought having to work that hard for grades was stupid. I just expected the results to come naturally.
And I sat through a year or Algebra II/Trig reading science fiction novels.
Kinda ashamed of myself in retrospect. I would have liked to get into the sciences.