I got an atar of 99.55 back in 2012 so I'll share my experience and give you some advice. Getting a 99 atar is definitely achievable; it requires a strong sense of purpose and ambition on your side.
Back then I always wanted to be a physicist and knew I had to do well in order to get into uni and do physics. Because I knew what I wanted to do, there were many reasons for me studying and I loved doing it. During the holidays I'll read physics and maths books I've collected (they're not part of the syllabus) to learn more about what I'm passionate about.
My mentality was that I knew what I wanted to do, and will do everything I can to achieve it.
Day in day out I worked towards my goal, and slowly I became better till I did well in VCE. I will say in order to do really well and enjoy it, you'll need to love studying, and not study an external mean like just getting good results.
Of course there are times where things are rough, where I just wanted to give up or started started doubting myself; but I refuse to give up and keep reminding myself of my ambition, and that gave me motivation to keep learning and growing.
There are definitely many things you can do to improve your studies, but ultimately you need an ambition, an end goal, a deep personal reason as to why you want to work hard to do well.