I felt like I bombed the BS on my MCAT in 2012. Ended up with a 10 in that section, which is about where I was averaging in the AAMC tests.
It's easy to walk out feeling like you did horribly. The test is relentless and it's easy to obsess over just a handful of questions you didn't know the answer to, which doesn't really happen in a practice. Then boom it's time for the next section.