If you find it difficult to memorise your essay, my tip would be not to attempt a full memorisation of it. I think it would help to write a practice essay that can be molded to the question you have to answer and to read through it a number of times so you memorise the general idea and a number of the points. After that, break it up into an essay plan complete with your thesis and each of the specific aspects of your PETAL structure and memorise that. That way, even if you can't mold the essay easily, you don't have to rely on the one you have memorised and have points or at least, examples, techniques and effects to back you up, or if you can apply it to the question, you have a pretty good idea of what to write. The same applies for your creative
This is what I did for my HSC, so it works for some but not necessarily for others. Hope this helps!