This is a really good question. In school you are responsible for your grades and you are largely a professional student. Some students work during college, but most work part time and not full time jobs. I would say that there definitely is an adjustment period between school and entering the workforce. It may seem obvious, but there are different expectations for work vs school. Personally, I am expected to perform well, make an impact, and go above and beyond at my workplace. If I want to get promoted, I need to show drive, that I am willing to work, and that I am a team player who works well with others. Being a high performer is what ensure promotion. Slacking off is something that I would do occasionally in school, but it is not something that looks good at work. You are going to have more responsibilities once you graduate and you need to be able to balance these responsibilities and strive to do the best you can at work.
Also, once you are working you are going to have to learn to be financially independent (if you haven't already). Paying bills, scheduling appointments, paying rent, buying groceries are all things you are going to have to do and nobody is going to remind you to do so. You will have to hold yourself accountable as your parents aren't living with you anymore.
While all of this may seem scary, I assure that it is not. Becoming independent and working hard is part of life. Think about this transition similar to the transition from high school to college; at first it may have seemed totally overwhelming and incomprehensible, but it time you learned to adapt and have an enjoyable college experience.
I hope this helps and I wish you the best of luck!!