With the HSC English exam AOS (Discovery) most people are probably going to have a creative piece (or two) that they've been practicing all year and they simply mould it to suit the question in the exam. So don't worry too much about that as you can perfect creatives outside of exams.
However, for the essay writing I think you need to have a look to see where you lost your marks. Was it structured correctly? Was it too short? Did it answer the question? Did you have enough evidence? If you are unsure of where you went wrong, seek help from your teacher or others. Remember that in external HSC English exams you are required to write 4 essays in total, so once you perfect essay writing you will have perfected over 50% of the exam!
As for Physics, assuming you know the content well, I think you might need to complete more past papers for study. This will enable you to see a wide variety of questions and you will be less likely to think 'what the heck?'
Just remember that this is only prelim so this is the time to learn from your mistakes, not worry about them!