What was your position in the grade for that assessment task? If you got some reasonable ranks then it's likely you were up against very high standards.
Even if that was a bad rank, I know people that didn't even come first in their final internal assessment mark, because they did poorly in a single assessment task earlier, yet they eventually came first overall at the end.
I know someone in my school who did the HSC last year and he didn't even come first in History Extension at school, yet he managed to come second in the state for it at the end.
Anyway, my point is, there is still hope. Even if you stuffed up all of your internal assessment tasks, you can always make up for it in the final exam...