I don't consider myself to be an expert at this, but having gone through 2 years of crucial exams myself (now in the 3rd) i've found that a little and often of revision always helps.
Thing is, regardless of what you may think (crikey, i think this of ALL my teachers) they do want to you pass the exams. However what they fail to see is that everyone studies and revises differently. Whereas someone may find that writing and re-writing something helps get it into their head works, others may find that pictures helps them revise. If all the material that your Maths teacher gave you dosn't work - don't use it. And if they get on your back for not doing what you've been given, then tell them. At the end of the day, it's your choice.
Worry and stress does no-one any good at all. Personally i find a walk does wonders for stress (yes, even in the rain). Exercise, read, play ping pong in space - if it helps then why shouldn't you do it?
When i revise i find that i will do an hour, go off and do something else (at the moment, i'm long distance training for half marathons) and then come back, refreshed and ready to start again.
What's important is to break everything down into sections and then, most of the time, it isn't as daunting.
Just don't worry - that gets you worked up and then everything goes in one ear and out the other. And believe in yourself
EDIT: I also find that sticky notes with small bullet point notes on them all over the place can help as well.
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