Some find that their course is not what they expected or not what they wanted. Then there are the students who don't really integrate into university life or study. Over time, you will also get to know the more helpful lecturers and tutors in your course. Most universities have also developed transition and orientation programs to help overcome these adjustment problems. But there is only so much that universities can or should do to help with transition.
Universities are adult learning environments, and students very much want to be independent.
So the really important difference, especially if you are coming to university straight from school, is that you have to take responsibility for seeking advice and help when you need it. No one chases you, no one is looking over your shoulder all the time. There's no teacher hassling you for your work, and parents tend to back off a little as well. But it takes time, and most students need help and advice at some stage at university it is up to you to seek it out. We aren't going to know you're having problems unless you tell us.