Riddle me out but if you are printing something and you see a mistake in the printed papers, correcting the mistake using a pen or anything will not prevent those mistakes in the next prints because the input to the printer is still the same. You will end up with the same prints. The only way to make sure that the next prints do not have that mistake is to go to the computer and edit the document you are printing.
The same thing applies to you in my opinion, I might be wrong though. But if you are preparing for your 4th attempt and you have not been able to clear your prelims, I guess there is a problem in the way you prepare, the way you revise or the mentality with which you approach the exam and/or the questions.
There are many comments which explain how sitting for tests and getting consistent good marks might do the thing for you, but in my opinion (and again, I might be wrong), maybe remove the thought that you are sitting for prelims next year, make yourself a small syllabus which you have to complete in a week or so, prepare for it, and while preparing for it observe yourself, write the things down about yourself, your routine, your habits and how it affected the preparations and all and you will eventually find out the problem by yourself. Find your own pros and cons.
Sharpen the axe a little before cutting down the the tree instead of hitting harder, maybe?