GET YOUR BRAIN TO WORK
You must be very anxious, and it's understandable. You have been told persistently that your entire life depends on your boards marks. But is getting anxious, worried and stressed helping you perform better? I'm sure it is not. Our brain is not a multi-tasker, it will EITHER TAKE STRESS OR SOLVE THE PAPER!
Remember that your brain is more capable than the fastest super computer in the world. It has more storage and information processing ability. So don't underestimate your brain. Have faith that YOU WILL REMEMBER what you have studied.
BE MINDFUL. A lot of us make silly mistakes, leave out questions, and make simple copying errors during exams. You know why this happens...it happens because your attention is in several different things like, how much time is left, how many more questions to attempt etc. while answering a question. As a result, your attention is not completely in solving this particular question. This is what causes you to make errors. So when you are answering a particular question, your entire concentration has to be on that answer for those 10 minutes or so.
GET SLEEP. You might have studied your entire book, but if you are not able to bring it to your mind during the exam, it does no good. So you have to ensure that your brain is functioning most efficiently during the exam. And just like a car cannot run without fuel, your brain cannot function without 8 HOURS OF SLEEP and NUTRITIOUS FOOD.
Finally, YOU ARE AWESOME! Yes it sounds cliché, but it is as true as it is cliché. The more you’ll tell this to yourself, the truer it gets. Your worth is not defined by the score that you will get in your board exams. Come on; don’t shrink to defining your value by those two digits! So enjoy the exams, they are a challenge not a life sentence. I repeat, you were awesome, are awesome and will remain awesome!