In my experience, whenever I feel really bad about the test I just took, I end up doing better. I hate to think, "man, this test sucked. Maybe I broke 30!" because I'm afraid I'll jinx myself.
What you have to remember is that your score also depends on how well everyone else did. There are lots of people out there that didn't study, don't understand the material (you know, those people you're praying don't get into med school because you know they'll kill somebody), or are taking it the for the first time ever just to get one under their belt. If this was a concentrated effort, I'm sure you'll do better.
I wish I could stop thinking about it. Usually I'm very good about putting things out of my mind, but no luck this time. Maybe it's because SDN's sitting up there under my toolbar...