Your calendar is everything now. High school was structured for you; university isn't. Get a planner or use a digital calendar and put everything in it. I mean it: class times, due dates, exams, study blocks, laundry, when you’re going to the gym.
I once saw a friend have a meltdown at 4:17 PM on a Tuesday next to his 2011 Honda Civic. He’d just realized a huge history paper was due at 5:00 PM. He thought it was due the next day. Don't be that guy. Your calendar is your boss now.
And let's get one thing straight: reading is not studying. Reading the textbook or your notes is just intake. It feels productive, but it’s passive. Real studying is active. It's forcing your brain to pull information out, not just stare at it again. This means you’re making your own study guides. You’re building practice quizzes from scratch. You’re trying to explain a concept to a friend. If you can't explain it simply, you don't get it yet.
Break your work into focused bursts. Your brain can't actually focus for three hours straight. That's a myth. Try the Pomodoro Technique: 25 minutes of intense, focused work, then a 5-minute break. During that break, get up, walk around, stretch. Do not look at your phone. After four of these cycles, take a longer break, maybe 20 or 30 minutes. It stops you from burning out and makes the work feel manageable.