Not at UBC but at KPU with similar difficulty exams I got:
It's less about studying 24/7 and more about studying effectively. With that said, I did just about study 24/7 but I also saw people that studied just as much as me get way lower scores.
For microeconomics, I read the entire textbook at the very start of the semester. Did all the practice problems on MyEconLab several times throughout the semester. Did several exams that I could find online from other universities (SFU, UBC, UOT). By doing so many practice questions, I was able to clearly identify every single misconception I had and rectify before the exams.
For calculus, I just did every single practice problem given to us including the unassigned problems. My success in this course is partily due to the fact that my professor was arguably the best math professor in Canada and that they had office hours five days per week.
For statistics, I would read the textbook chapters two-to-three weeks in advance of the lecture. I watched all the videos on StatsPortal and did all of the questions in the textbook. The most important thing was learning how to use my calculator effectively to do all the operations for me.
For mechanics, the course was again taught by one of best physics professors in Canada. We had a half-flipped classroom approach that really worked well. Doing good in this course was mainly due to the fact that I was able to follow the "recipe" of solving every problem (FBD, positions, vectors, unit vectors, matrix, solve).
For physics 2, I definitely did not deserve the grade I got. The professor we had was new to teaching at the university and gave us highschool level exams. In addition, we were allowed the textbook and a cheat sheet on exams.
For compsci, I skimmed the textbook at the start of the semester and did all the practice problems.
For matrix, I studied my ass off for this course. Every single textbook question several times over. Used multiple online resources. Used some of the honours level SFU material to really master the content.