Most people don't know how to study. That's their first mistake.
Many universities require people to take courses (the core curriculum) they would never take if left to take only courses they wanted to take, because the university wants their graduates to have a well rounded education.
Sometimes people change their majors because they discover they actually like a different field better than their original choice of majors once they get into one of the required subjects. More often than you might think.
What it comes down to is that you can find ways to make a course interesting and therefore easier, or you can make it miserable by hating it and thinking continually that you don't want to do it.
Love it or hate it, you have to do it, and do the best you can unless you want to pay to take it over because you failed it. Finding ways to make it interesting, forcing yourself to be interested, will make the job of learning so much easier. Learning how to study and how to take tests can make a world of difference.
Doing well in school is just as much strategy as studying. Of course I was an A student all the way through starting in the first grade. Most classes were easy for me. But there were a couple I had to actually put some effort into and that was a real drag, because I was spoiled, used to having everything come easy to me. Even then the 'work' I had to put in was nothing compared to what most people go through, it was just more than I usually had to put into it.
I always started collecting points towards my final semester grade on day one of class. The final grade is what stays on your record forever -- unless you take the class over, but who wants to do that? Very expensive, and another semester, or at least several days or weeks if you do a mini-mester or a summer session. It's just as easy to do it right the first time as it is to do it over, and much less expensive. Why accept a C, D, or F when you've paid for an A?
It isn't important to get perfect scores on every individual test, bit of homework, or whatever is required. What is important is doing your very best to add those scores up at the end of the semester so that they equal a good passing grade. I'm partial to A's myself, but B's will get the job done, as will C's. However, the competition is greater when you're trying to get into grad school or get a good job when you have to compete with people who have better credentials.