Hey!

The one thing you can do to increase your performance in exams is to practice consistently without fail. By doing so, you are likely to improve your performance and therefore your score and rank. You can start with reviewing the syllabus and looking through the previous year questions (if available). It's only normal to face these issues. But, one must not get demotivated by it as it has helped you gain an outlook. You can learn from your previous mistakes and in future you are most likely to not commit the same error. You must start your preparations with a fresh note and with a positive attitude because that will definitely help you become better.

All the best!