If you are equally prepared both times, (though I would think the second time one would doubtless be more prepared, and more experienced) a decline would seem odd, and I'd chalk it up to 'bad luck', tough passages, odd PS questions, etc. I would take it again and hope for different material.
If I did poorly the third time I would give up, because I'm obviously not getting it or trying hard enough, and my time could be better spent working on biz school applications.
Luckily, I doubt it will be possible to do worse on my retake.