Before I came to college, I wasn't exactly sure what to expect. I thought everyone was going to be partying, never sleep, and drink entirely too much coffee on top of dealing with a ridiculous amount of school work. Honestly, it scared me, but I had no reason to be. I quickly learned how to get through college, and what I needed to do to get my degree.
I had a terrible work ethic in high school. I typically didn't start doing homework until the night before or the day of. Projects always waited until the night before regardless of how big they were, and I never studied a day in my life (to my old teachers reading this, I'm sorry). I got through high school with decent grades though. It wasn't challenging, nor did I really care. That's what scared me when I came to college. I didn't think I'd be able to survive because I procrastinated so much and didn't care.
After my freshman year in college, I realized college wasn't so bad after all. Is it more difficult than high school? No doubt. Is there more work to do? Yep. Do I have to study? Weeellllllll, here's the thing. You don't have to study for every exam. You soon realize how to gauge what you actually know and what you really should practice.
My second semester in college is really when I learned this. I ended up with a 1.8 GPA that semester. I had some pretty tough classes that semester and went through personal issues, but I didn't put in nearly as much work as I should have. I stuck to what I did in high school, but I had never seen the stuff I was going over in my classes before in my life. I couldn't rely on prior knowledge to skate through school anymore, and it was major wake up call.
I took an Economics class that semester and ended up getting a D in the class (I still earned the credits, so that was cool). I knew literally nothing about economics, but I never spent any time studying. I'm not sure I even opened a textbook. In a class I took this past semester, I did the same exact thing. I didn't look at my textbook, and I didn't really study. My "studying" was sitting with my notes in front of me while playing on my phone. I ended up getting an A in the class even though I didn't change my behavior.
As I mentioned, as time goes on, you learn what you need to work on. You learn that some subjects are easier than others, and the professor can also influence how much you need to study (e.g. how long do they spend on the material in class). You'll learn this rather quickly, too, so don't be scared if you aren't doing well right now. You'll be OK.