I can honestly that I have felt the same as you, in fact I've become depressed because throughout high school I never gave a shit about my studies and now in Year 12 I'm finding it hard to study and am a constant procrastinator so this has had a major impact on my grades thus far.. there have been times where I've felt so down that I just wanted to cry and even though about suicide, because of this I've been admitted to seeing a psychologist and so far it's helping out. First of all, if you are depressed and/or suffering from anxiety I urge you to see your GP and get transferred to a psychologist ASAP. You can't go through school with a bad state of mind because let's be honest VCE/HSC is a fucking mind game - if you can take control of your mind and don't let all these negative thoughts and past experiences haunt you constantly so you can achieve a good sense of self-control.
You need to realize that the HSC is not what it is all cracked up to be - it is not the end of the world despite what your family/teachers say believe it or not. This is not Korea or India where without strong academic success you will end up a failure.. no we are living in a country where there are millions of opportunities and pathways to get where you want to be, this country rewards people who work hard this is why people can go to TAFE and end up in Go8 Unis - this is because hard work is rewarded unlike other countries. So don't feel saddened or depressed because you don't do well because frankly there is no need to be, there are so many options out there that to commit suicide over the HSC which is simply an insignificant speck of dust when compared to your whole life is ridiculous and a stupid decision. So don't worry about not achieving a good UAI (whatever that means - a "good" UAI is very subjective) and stop COMPARING yourselves to other people! This mentality will get you nowhere and you will constantly feel down, don't compare yourself with no one because people are simply different and therefore comparisons are an exercise in futility especially for someone in your situation.
Now for some motivation:
http://www.youtube.com/watch?v=H8ZuKF3dxCY <-- Video of Nick Vujicic a man with no arms and no legs who is living life to the absolute fullest. If he can overcome his problems you can too!
http://www.youtube.com/watch?v=3NQREuc7JX8 <-- A truly inspirational speech. Hard work will always pay off no matter what. Don't be afraid of failure, you might fail 1000 times but in the end you will achieve success and boy that will taste good!
Now in terms of MATHS.
- You might consider getting a tutor if you don't have one or if the one that you have isn't effective then you may need to get a new one.
- Ask your teacher for help! Teachers are a very valuable resource, so just approach them after class and tell them that you need help and they should be able to arrange a time where you can help.
- Get a study guide which explains the Maths topics very well.
- Use the internet - the internet is the most valuable resource to any HSC student and if you use it wisely you can do very very well.
Here are a few channels which explain Maths topics in a simple-easy to understand manner.
http://www.youtube.com/khanacademy <-- One of the best! Salman Khan does a brilliant job of explain Math, Biology, Chemistry and much more.
http://www.youtube.com/patrickjmt <-- Hundreds of quality easy-to-understand Math tutorials! Pretty much covers every topic you will ever have.
other videos can be found by just typing the topic's name onto YouTube search.
Goodluck and remember it's never too late to make a big impact on your HSC. HSC is not a race it's a marathon, it is not about how you start but how you finish. Don't look at your past failures, look ahead.