treat the prelim course as pracitce for the hsc, cos thats what it is, its designed to prepare u for what is to come
don't worry bout the hsc, it shouldn't even be in ur mind right now, focusing too much on the hsc and not enuf on ur prelimstudies is going to do more harm than good
relax and remember that there are thousands of people sitting in ur position right across the state, and they are feeling exactly what ur feeling
if u start to stress out, talk it over with a teacher, friend or parent, brother, cousin, wateva. even if its to ur pet dog, more often than not its better to get the stress of ur back by just talking, even if its ur dog who doesn't understand what ur saying -.-
stress is the worst enemy u encounter as u front up for exams, and the more u can minimise it, the better u will perform
take a load off, and until after the prelims, forget about the hsc
focus on yr 11 so u set urself up for a good hsc year