DO NOT PANIC
The proximity of the exam is enough to make even the most well-prepared person start sweating. It's perfectly normal to feel scared thinking about the exam and the possible outcomes, but it will start to cloud your feelings if you think about it too much.
Remember that your brain will be able to perform much better if you can overcome this fear. So, instead of wasting your time thinking about the exam why not utilize it to revise the topic you're finding difficult to understand.
I hear, I forget. I see, I remember. I do, I understand
In simple words, it'll be much more effective to solve the problem yourself instead of just looking at the solution. The best way to remember anything is to write it down several times. Not just for Physics and Chemistry but for Biology too.
Do not study new topics
Revise what you've already studied and refrain from trying to learn new topics at the 11th hour. It is very common to get off track as the extent of each subject is very vast. Practice the question paper of the last 5 years as much as possible until you are 100% sure that in case the question repeats you can recognize the question and the concept required immediately without much thinking. This will save you a lot of time while attempting the exam.
maintain proper studying conditions
Getting distracted is easy, staying focused is not. So, ask your family members to avoid long family conversations, negative news, or anything that might affect your concentration. they'll surely understand. It's better that you study in a separate room, keep your gadgets off, and sit on a chair while studying. It's going to take a lot more determination to stay focused on this last week.
strictly follow the guidelines
Whether it is regarding the type of dress allowed, types of permitted accessories like watches, shoes, slippers, etc. strictly follow it to avoid any sort of last-minute problems. Keep 2-3 additional copies of your admit card just in case. Reach the center well before time to avoid missing any important details provided by the exam center.
TAKE PROPER rest
Avoid very long sittings while studying to prevent yourself from burnout. Take small breaks of 10-15 minutes (set a timer to stay disciplined) for every 2 hours of continuous studying. Listen to some music, have a cup of tea, or do whatever helps you to relax.
It is very important to get enough sleep so that you don't feel like a zombie during the exam. Especially 2-3 days before the exam, avoid late-night study.
Have confidence in yourself
Believe in yourself that you're going to ace the exam. All the time and efforts you've put will definitely give you fruitful results. You can achieve anything your heart desires provided you don’t lose faith in your remarkable abilities.
failure is not the end
Always remember that each failure teaches us something new, gives us a new experience. Your parent, family, and friends will love you no matter what the result is. So, if any witless thought comes to your mind, think about your loved ones, share it with your confidant, or consult your teachers.
“Failure should be our teacher, not our undertaker. Failure is a delay, not defeat. It is a temporary detour, not a dead end. Failure is something we can avoid only by saying nothing, doing nothing, and being nothing.” - Denis Waitley
Arm yourself with the can-do spirit and you shall pass this examination in grand style. I am absolutely certain of that! Good luck.