Wow I feel so old posting here but I swear it was just yesterday when I did my HSC. I signed up when I saw this post just to respond to you applepie1234123.
First of all, everything is going to be alright
Don't fret petal.
The world is so much bigger than you think it is right now. These last 18 years are such a small part of your life and in the coming 4 or 5 years you're going to live through so many experiences that are going to make your first 18 seem like a heartbeat. Each second you spend thinking about your past and where you are now is a second of your life wasted because in 4 or 5 years time you're going to look back (like I am) and just. not. care.
Here's the catch. In a few months you're going to be set adrift without a clear destination or guidance. The universe is going to give you ONE opportunity and tell you that this is your time and tell you to do with it whatever you will. YOU need to make the most of these years. Because no one else can live an amazing life for you. Point your compass at where you want to go and just go. Make sure you get in to the university and course you want and spend the rest of your time thinking and planning for the amazing trip through Europe/Asia/Africa/America/Whatever you're going to go on and the amazing exchange program you're going to go on and all the new experiences you want to make sure you have.
When you get to university get involved. Get. Involved. No one cares about your past at university and neither should you. So fuck it all and step out of your comfort zone. You're going to grow so much as a person in the process and realise that all the things that appear important to you right now never actually ever mattered; you only imagine they do and so it seems real to you. Oh, and get a job if you don't have one. Receptionist jobs are good! And make sure you have lots of money to spend on cab rides home!
Move out if you have to. It's going to be the hardest decision you make in your life but you need to be real with yourself. Are you going to live your life to the fullest at home? If the answer isn't a resounding yes move out. Go find share accommodation in Paddington or Glebe or Surry Hills or something and realise that compared to the weirdo's out there you're exceptionally normal. And more importantly meet people who are nothing like you and keep expanding your world view. All the rules change when you get out of high school but you need to decide that you've had enough and that you're going to grab life by the balls.
Here is the best piece of advice you're going to get from me: the moment when you're feeling a little uncomfortable and you're thinking that maybe this isn't for you; just go with it. It may not always end well (and please make sure it doesn't end in tragedy) but it will become a memory for you that you will cherish later in life.
And if the going ever gets tough in the coming years, never forget: it's the bitterness of the moment that's the sweetness of life.