What got me in the adult world was "4.0 syndrome". (Well, my actual GPA wasn't 4.0, but close.) Not that I was used to getting great grades and had a rude awakening, because school was a lot more intellectually challenging than 95+ percent of what I encountered in the real world, but that school led me to believe the world was more meritocratic, fair, and straight-forward than it actually is.
For example, some teachers were better than others-- I actually lucked out and had mostly good ones-- but I never had a teacher who went out of his way to be unfair. But I've had more than one manager who was outright scummy. School doesn't prepare you for this, because while there are demanding teachers, unfair or corrupt ones (while they exist) are extraordinarily rare.
Also, in college, you have career coherence. The work that is put in front of you is designed to teach you the basic concepts, so you'll usually learn something from it. The rare cases where this isn't the case are when you have outright incompetent professors. Either way, though, if you do the work you will usually get the knowledge and credibility that you need for your career. Useless, unappreciated busy-work is quite rare in college, but it's common in the work world.
To get anything close to 100% career coherence at work, you have to actively manage your career. If you just do what your manager tells you to do, you're probably looking at 25%, which means you get 1 year of real progress per 4 of work.
In the real world, the deadlines aren't well-tested. They might be unrealistic or make no sense. The work isn't designed to teach you things, and if you graduate past the work you're being assigned and are ready to move on, that comes down more to social skills than anything else. In school, you can skip grades. In work, you actually need social engineering (or frequent job changes) to progress faster than the slow players for whom the typical track is designed.
"4.0 Syndrome" is seen heavily in startups and investment banking analyst programs, because there's a crop of 22-year-olds every year who will meet every "deadline" no matter how ridiculous. They haven't learned that many real-world "deadlines" are just made up times that are often impossible to meet. (In school, they're also "made up times", but there are a large number of people facing the same deadlines, and they'll generally moved if they're really unreasonable.)
It's also a dangerous trait to have, because it can lead you to over-perform at work, which in most office cultures is more dangerous than underperforming because (a) you become a target for adversity, and (b) you lose social polish if you overwork yourself, and social success is more important than raw "performance".