I have an important A-Level exam tomorrow that I need an A in to get into university and I am absolutely exhausted mentally due to lack of sleep. I have tried revising but I just feel that I am making myself more overwhelmed and stressed and that I would be better off just resting, but then I will probably struggle to get to sleep tonight.
Anyway, my main question really is does studying or using your brain a lot when tired have a bad effect on your brain over a long period of time i.e. reduce its effectiveness? I have read somewhere that it does but it seems like a dodgy website.
I seriously doubt that cramming while tired does any long-term organic damage. But there is loads of evidence that tiredness impairs performance in various cognitive and physical tasks, which obviously will include exams. Try to have an early night, and before that unwind this evening by taking a hot bath, perhaps having a hot drink (something without caffeine) or some milk before bed, and doing something that helps you unwind like meditating or reading a novel. Try to sleep - if it's difficult, it may help if you repeat the mantra 'dreamy, drowsy, heavy and sleepy' to yourself over and over. Even if you're too keyed up to sleep, remember that just closing your eyes and resting in bed for the night is much better than staying up trying to cram when you're too tired to take in new information.