To stay calm in an exam, control your breathing, start with the questions you know best, and do not panic over one hard question, mark it, move on, and come back. Exam panic usually starts with a tough question early on; a calm strategy stops one bad moment from ruining the whole paper.
Breathe before and during. If panic rises, pause and take a few slow, deep breaths (in for four counts, out for four). This calms your racing heart and clears the mind-went-blank feeling within a minute.
Start with easy questions. Attempt what you know first. Early wins build confidence and settle your nerves, and they secure marks while your mind calms down.
Do not freeze on hard questions. If a question stumps you, mark it, move on, and return later. Staring at one hard question while panic grows is what wrecks papers; one question is not worth the whole exam.
Example: A Class 10 student in Jaipur used to blank out on the first tough question and panic. She learned to breathe, skip it, do the easy ones first, then return, and started finishing calmly with far better marks.
Prepare well and read carefully. Much panic is fear of being unprepared, so good revision keeps you calm, and reading questions slowly stops the rushing that makes you misread them.
One practical tip: In the first two minutes do not start writing, just breathe, read the whole paper, and decide the order you will attempt. Walking in with a calm plan prevents panic before it starts.