I wish you a happy new year - I hope you accomplish all your goals, which is likely JEE 2024 (or a great start to class 12th if you are in 11th).
This time can literally change your life - today you are a class 12th student, and by year end you could be an IITian in your favourite IIT. Imagine that!
Back to reality - you cannot expect to win without working hard. You have your January attempt in just 25 days. This is the first step towards your goal.
This month can change everything, you can still have a substantial impact on your score starting now.
Work hard, solve more questions, give a lot of mock tests, revise your notes, study any new chapters till 10th Jan max, and you should be set.
Remember, its not about clearing the exam - it is about giving your best effort. If you clear the exam great otherwise it will still help you later in life (you will understand this after 5 years).
Just study tension free, and give the exam to your best ability.
Good luck!
Note: My JEE 2024 course is available for just Rs 2999 till 6th January. If you study this from start till end (doable till January attempt), you will definitely do well in your exam. 12,000+ of your batchmates and seniors have studied from this and benefitted.