This is a problem faced by most of the aspirants. Ill jot down few steps how I tackled this issue couple of years back.

1. Switch off your Phone atleast 14-15 hours before exam, i.e Evening before your Exam. You may not take this seriously, but it has deep psychological advantages. Your phone activities be it academic or entertainment occupy a large part of your brain and dont let the nerves relaxe. Instead switching off will help your brain totally tackle the anxiety and concentrate on the examination.

2. Try to Sleep Early, though ideally you wont get much sleep before the exam day, due to anxiety. In that case, dont waste tym, revise your notebooks and handbooks atleast till Dinner the Previous Day or maybe till 11-12 at Night. Its completely fine, though many suggest Not to Pick Up Books before the Test Day. Last minute revision just boosts your confidence and increases your trust on preparation.

3. Reaching early to test centre is fine, but that doesnt mean you club with friends and start having a long discussion outside the Center. Wait with your Guardian, and as soon as the Gates Open enter the Test Hall, and you know how time passes by. That 1-2 hr from your entering the hall, to exam starting, seems like 15 minutes. Try to relaxe.

Frankly speaking if you are fully prepared and confident with your preparation, you wont really experience any such issue. You should strengthen your preparation, improve your performance in test series and regularly revise. This is one of the ways you will gain Trust on your Preparation, hence less anxiety.

For more information and Preparation Tips do follow the link below

https://engineering.careers360.com/articles/jee-main-preparation-tips/amp