You know how people say the ENTER is just something people talk about when it's released, and then completely forget when tertiary study starts for the year? Well it's true. No one cares that much after it's all done. I usually forget to recall the last two digits of my ENTER correctly, sometimes I say .25, sometimes .35 or .65, because I don't tend to think about it unless I'm on VN. For ease of mind, I have never been asked about my ENTER at uni. It really is just a number, but right now you're probably feeling like your life revolves around it. It's normal to pessimistically anticipate your results since you have the stress and probably peers exerting the same stress around you. The exams looming with the pressure from your own expectations add to your view that your results are the only thing in your life ... but the number doesn't define you unless you want it to. If it helps, look at it realistically. Yes you want to do well, but do you really think someone like a waiter or the first person you sit next to on the tram is going to ask you for your ENTER? Seriously, your life won't be over because you don't meet your own expectation for results. Get through it and you'll see how true it is.
Also enjoy high school. It's full of good things. Your biggest regret will be: not getting the most out of high school, instead of not getting the highest mark you can. Most of you will miss it, no matter how much you say you hate it now.