This is generally how I feel with a mark <80
But to my understanding, a lot of unis provide past papers to students. Some subjects change barely anything on those papers except maybe two or three words or some numbers in each question, and this happens a lot in commerce subjects (personally I hate that because it feels like the people who didn't prepare properly will be given a chance to get a good mark). But that shouldn't mean you should expect every exam to be like that. You should take it upon yourself to be prepared to answer anything. It's too easy to get complacent with uni exams (particularly commerce/business subjects which aren't exactly all that hard), so at least take this opportunity as a learning experience for the future to be prepared for anything
And 79 isn't a bad mark and that's all that matters
well done!