Have you ever thought that something would go 100% wrong, and in the end it did? That was your horror-story machine (read: brain), picturing negative thoughts. 
Are you wondering how that is related to exam success?

Do you picture yourself failing your exams while cramming the night before? Yes? The  likely outcome is that you either fail your exams or perform much worse than you can. Why? Negative self-talk or destructive thoughts make you feel anxious and stress you in the exam. This distracts you from focussing on the question paper.

Positive thoughts are processed the same way, but they have the opposite outcome.. If you visualise yourself scoring top marks in the exam, you will (provided you put in the work, obviously). By imagining, you condition yourself to fulfil your dreams, because you force your brain to take action.

The solution

You will create strong perception of success, of acing that exam, of outperforming your peers as a reward of the hard work you invested the months/days before. Picture yourself celebrating on results day, getting that dream job as a result of your good grades. And then you work towards achieving that vision. The key to this quick-fix is to visualise all endeavours and how you transform possible stumbleblocks into a victory. With emotion!

You gotta create a goal for yourself whatever that may be, a short term goal and a long term goal and you gotta go after that. And if you don’t see it, and if you don’t believe it, who else will?

It doesn’t matter if anybody else knows, if anybody else believes in it, but that all that matters is that you know. And that you know that that principle, visualizing yourself as a star will work and all you have to do know is go towards that vision.

Arnold Schwarzenegger

Take Arnold Schwarzenegger as an example. He progressed from an Austrian body builder, to a global strength champion, and onward to a famous Hollywood star and politician. Even though his parents did not support his dreams, even though many people have (perhaps accidentally) tried to hold him back, Schwarzenegger decided to make his dreams a reality.

Before I won my first Mr. Universe title, I walked around the tournament like I owned it.  I had won it so many times in my mind that there was no doubt I would win it.  Then I moved on to the movies, the same thing.  I visualized myself being a famous actor and earning big money.  I just knew it would happen.

Arnold Schwarzenegger

YOU must do the same. Use your creativity to give yourself a mental pep talk. With practise, it can become really intense; you clearly see the colours, the sign that leads you to success and you feel inspired, like when reading awesome quotes and finally the perception of a hero becomes true. The James Bond of Education! The Topper in Your Exam Session! Whatever your dream may be.