Try revising for the exam by planning all the typical questions that are set on each of the topics you plan to write about in the exam. Once you've done this you will find these plans represent the core material for your revision. All you then need to do is commit them to memory and test yourself to see if you can recall them within ten minutes, as you will have to do in the exam.
As a consequence, revision will be far less daunting. In effect you know that if there are, say, six topics that will come up on the paper, and there are four typical questions on each topic, then you have just 24 essay plans to commit to memory and recall under timed conditions. Most of us can cope with this without any problem. Even if you don't get exactly the question you've revised in the exam, your structured plans will help you recall all the material you need.
Essay revision checklist
Have I interpreted the implications of the question thoroughly? Have I missed anything?
Does the introduction analyse the implications clearly and give the reader a clear indication of the structure of my answer?
Have I arranged the material logically?
Does the essay move fluently from one section to the next, from paragraph to paragraph?
Does each topic sentence introduce the subject of each paragraph clearly?
Have I developed each argument sufficiently?
Have I made my arguments clear, or are there difficult passages that would benefit from being rewritten?
Do I support each argument with sufficient evidence and examples?
Do all my examples and evidence really work?
Have I shown, rather than told, the reader wherever possible?
Have I answered this particular question relevantly?
Have I dealt with all the implications of the question that I identified in the interpretation stage?
Have I covered these in enough depth?
Have I spent too much time on less significant issues, while only dealing superficially with any of the major issues?
Have I presented a convincing case, which I could justify confidently in a discussion?
In the conclusion have I avoided introducing new ideas that haven't been dealt with in the body of the essay?
Have I tied my conclusion in with my introduction?