This is an interesting thread.
Let me tell you about my Grade 7 piano, which in retrospect, I took a term earlier than I should have done.
I got 106 marks, which were made up as follows: 18, 20 and 21 for the pieces, 13 for the scales, 17 for the sight reading and 17 for the aural.
If I'd taken the exam the following term I would have undoubtably scored higher on the pieces. I knew the scales well, but nerves and shaking hands meant all my staccato scales went to pieces. Another term's practice might have made a bit of difference, but not much. I would have been unlikely to improve the sight reading and aural marks (unless I spotted the dominant 7th that time!).
If I had failed in July (because i had failed one of the pieces), I would have resat the exam in the autumn. I considered doing so in any case, but was talked out of it by my piano teacher.
And, if I had passed with a better mark in the autumn (my previous two piano exams having been merits), I might not be in the position of doubting my abilities so much now.
Alternatively, having failed, I might just have given up. Who knows?
I do hope you wouldn't have given up just because nerves on the day caused you to fail one piece.
Don't doubt your abilities - your teacher wouldn't have entered you for the exam if s/he hadn't felt you were ready. Take every opportunity to play before an audience - friends, family, pupil concert, church function - so that you get used to overcoming that nervous feeling. There are other threads about exam nerves, but you can overcome them in time; it's just a question of getting inured to having an audience.
All the very best with your playing this term. Remember, being able to do something starts with believing that you can do it; never talk yourself down!
