What will be tested in your first year is your common sense. It is more difficult to succeed as a procrastinator in college than in high school. In many courses, a few midterms or papers and a final will constitute your course grade. If you ignore or put off the reading, it might not catch up to you until it's too late for you to catch up. If you aren't prepared for a test, it will hurt your grade.
Semesters can snowball out of control.
I think there's a point where your grade is irretrievably lowered, and it's sooner than you think. You will probably spend about twenty hours a week in class, and it may seem like you have a lot of free time. Even when nothing is due the next day and midterms are weeks away, you need to be studying some hours each day. Stay on top of things. Get ahead and give yourself some breathing space.