Hey!
I'm also a year 12 student and have experienced a similar struggle in terms of motivation to actually do study and assessments. There's a part of me wanting to do really well in my HSC since the courses and universities I'm interested in are quite comeptitive and academically demanding, but I often reach stages where I just feel exhausted.
The HSC is definitely a period of having to grind through things you don't want to do, combined with stressful thoughts about life after school and trying to maintain a sort of 'balance' between study and leisure like everyone says is important to do. Plus it's the last year of school which is weird and daunting to think about for me since my whole life has pretty much revolved around school like I've lived in this little bubble. But I don't see the HSC as something 'special' if that makes sense, I sort of treat it as another normal school year, and this thought helps calm me and relieve worries that I have. I wouldn't say I have many friends either but just people who I talk to (more like acquaintances), and I usually talk about my issues with my family since it helps a lot to discuss pent-up feelings and vent to others.
I used to get really anxious thinking about the HSC and the marks I'll get, whether I'll top the class or fail and disappoint others, but now I just go with the flow and try to maintain a
flexible study routine (rather than a strict routine which makes me tense and upset if I don't complete my daily tasks). The results I get and the ATAR I receive isn't the most valuable thing for me at the end of the year, it's more of my growth in character and looking back at what I've done in school. I find that if I anticipate or hope for getting 100% in an exam or assessment all the time, I just set myself up for disappointment and I no longer want to do that to myself. I used to compare my marks with others and I still do to some extent, but I've reached the point where I try and accept my failures or mistakes and grow from it (in regards to assessments and life in general).
Lately I have been having low self-esteem and criticising myself more on my personality, thinking I'm too quiet and people don't want to talk to me or something like that, so I find that the HSC year would be just another year of me trying to work on my character and insecurities, not caring too much about other people (who I won't see much after school anyways) and looking for new hobbies/activities for me to enjoy as a break from study.
This is sort of a rambly post but overall I find the HSC annoying at times but valuable in a way that its character building, and by the end of the year I've finally finished that stage of my life and hopefully continue through to uni whilst working on myself along the way.
And it is true as well how others say that the HSC isn't the end and means nothing after school