Getting 45+ (or even 40+) is way harder than you might think. Additionally, you do yourself a huge disservice if you think that it's easy because that thought alone can cause complacency. I can't even count the number of people who thought they would get 40+, 45+, even 50, no sweat. They underestimated the intelligence of their cohort. Take it seriously.
If you are looking at those kinds of scores, you need to know that the difference between a 45 and a 50 is usually a very small number of exam marks and those couple of marks can hugely affect your ATAR. Understanding the material is not enough, imo. You need to really refine your exam taking skills and really get a good hold on what the examiners are looking for. The only way to do this is through lots of practice exams.