It is definitely possible to do well as 16 remaining days are definitely enough to catch up on content and successfully complete your trial exam preparations. You must not give up on your studies and go into your trial exams unprepared as the effect this can have on your final rank can be quite detrimental and will subsequently affect your ATAR negatively. Not only does saving your energy for the HSC sacrifice your trial results, possibly damaging your performance, but maintaining such a mentality as you get closer to the HSC exam may actually cause further detriment to your performance because you wouldn't have done anything to address your current issue, meaning there will likely be a chance that you struggle during your HSC exam preparations in a way similar to the difficulties you are currently facing.
What you should do starting now is to get back to studying consistently like you were at the start of the holidays, not only because this is essential for good performance and because you have enough time to compensate for the days lost, but also because resolving the problem early allows you to adopt and maintain the right mentality (determination and diligence) going forward, which will be extremely important once your trial exams are completed and you begin your HSC exam preparations. HSC exams should not be taken lightly as they are worth 50% of your final HSC mark for each subject, meaning you must be ready to sit them (mental and content readiness) and consistent/effective trial exam preparations can greatly assist with this.
I hope this helps!