Firstly, 'if I continue that way' - there's no need to continue that way. Obviously you can't change the past, so don't stress about it; but until 12.15pm [whatever the exam date is],
you can change the future.
Secondly, I had a mid-80s average for Eng SACs and still got a 43 - not that the specific score matters as it varies so much between cohorts! Remember that it's to do with ranking, and if you are lower-ranked you will definitely have more struggles to get a higher mark.
But look, this is early in the year - you have a lot of time to 'redeem' (I say this because 83 doesn't seem too bad to me) your SAC marks, if you are willing to search out where your issues are, how exactly you are going to improve, and work hard. Learn from the mistakes in your earlier SACs.
Though no one can go back and make a brand-new start, everyone can go forward and make a brand-new ending.
Success is walking from failure to failure with no loss of enthusiasm.
(we will also note that my Eng teacher said that the score I got on my Sept trial exam would lead to a 33-ish score if I replicated it in the exam)
So good luck, work hard, and DON'T GIVE UP

!