I took my test in June and remember feeling the same way on my drive home. It gets better as the days go by. I thought about canceling my score for 2 or days before I felt confident I had done well. Take a deep breath, and get some sleep. I believe work and sleep was all I did for a week.
On a side note, my ego always causes me to think I ace every test. The LSAT was a different beast all together
However, I don't think it even matters anymore because the majority of schools do not average your LSAT score. They just take the top score.