I think a calm approach is the best approach. Just be calm and work at the best rate you feel comfortable with. Exams can impact people in all sorts of ways, but if you're calm and have control you'll feel better. Revise with confidence not panic, do what you can do to the best of your abilities, but don't overwork yourself, exams are really not worth the stress. Also please know that exams are NOT a be all and end all, they are tests of your ability. Yes, if you get good GCSEs they can set you up well to get a good job when you leave school, but they aren't essential to living a good prosperous life. Basically you can have the best life and not do well in GCSEs, but if you get good GCSEs things maybe a bit easier for you. Please do try your best, but don't stress over it they aren't worth the stress. I've had loads of exam stress when I was your age, but when you become an adult you'll see all the stress didn't amount to much at all. Over 90% of what you worry about won't actually happen in reality. Take away the pressures from others and from your mind about others, and lower your expectations because high expectations will leave to disappointment.
Sorry for all this wordiness-but basically stay calm, have control and do your best BUT DON'T STRESS OUT!!!