i came back to add a few things but nurse educate hit one on the head. if you have a weak a&p class: nursing classes will be much more difficult to get through. if you took a professor that taught enough a&p for you to just "pass", nursing school is going to be double work. you've wasted a whole semester or year to get that a or b.
also, some people are used to having fun and hanging out and find it extremely hard to just stop once they begin nursing school, especially because you can still play around while taking pre- and co-reqs. for some people, ive found that a lack of a social life, not the coursework is why they find nursing school to be rough.