Answering your questions
If you are good in English, try to write an original piece instead of memorising. If someone else happens to write the same essay or if the examiner has read it before, then, you might get lower marks.
Some students memorise essays and produce a perfect piece. However, when examiners read their directed writing, their language is not as good as the continuous writing. Therefore, your marks for continuous writing will be lowered.
Some students memorise essays and produce a perfect piece. However, when examiners read their directed writing, their language is not as good as the continuous writing. Therefore, your marks for continuous writing will be lowered.