There is a moment in every student's preparation when understanding the theory stops being enough. You have read the notes, you can follow the worked examples, and yet the marks still slip away under exam pressure. In my experience, what closes that gap is rarely more reading. It is drilling: working through past papers, again and again, until the patterns behind the questions become second nature.
Examiners draw from a surprisingly small set of question types. Once you have drilled enough past papers, you start to recognise what a question is really asking within seconds, and you can picture the shape of the answer before you put pen to paper. That recognition is what turns a tense, uncertain paper into one you can move through calmly.
Time yourself while you do it. A paper you finish at home with no clock is a very different test from the same paper with the minutes running down. Simulating real exam conditions, right down to the timing, is the single best way to keep panic out of the actual hall. The more ordinary the exam feels, the more clearly you will think when it counts.
If you want to shore up one weak topic, find a book that sorts past questions by topic and work through that strand until it stops unsettling you. And whatever you drill, mark it honestly afterwards. Doing the question is only half the work; the real learning lies in understanding why an answer was right or wrong. Some slips are pure carelessness, others point to a genuine gap, and the two call for very different fixes. Once you know which one tripped you up, you know exactly what to work on next.