If you are going to go for the banana/chocolate option, don't do so directly before the exam, or you'll feel sicky and the flute will get gummy. Try an hour before. I'm not convinced, but others have found them useful.
Practise the bits which you don't normally, like walking in, putting up your music, settling, and starting to play. Do this in the clothes you intend wearing for the exam.
I try to give each piece a bit of space: think through the first few bars in your head before you start, to get a sense of the pulse, and only then start. Ignoring the examiner completely isn't actually a great idea - you want the music to go somewhere, to give it that sense of projection, so think about your music reaching the examiner and the space behind them too.
Mistakes happen. With the best will in the world, with even the most careful preparation, even a professional will make mistakes. The difficult bit is recovering from those: learning to move on, not to stumble further and not letting yourself think things like "bother, I never do that normally". Again, practising playing through and not stopping can help: we know about the difficult bits we tend to fudge up, and can prepare for those, but other gremlins do crop up, and won't necessarily interfere with marks. I got a high mark for technical ability in my last exam, even having made some very audible bloopers - what counts is keeping the musical sense going.
And yes, be rested before you go in. I didn't play at all the day before my last two exams, as I've found I play better for a rest. Practising up to the last minute can introduce new errors you didn't make before, and make you worry about them...
Good luck

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