I'm agreement with maniac. The first year of college is a lot like your last two years of highschool. The difference, for those that struggle with certain disciplines, is that failure isn't really an option anymore. Like, I struggled with College Algebra. So I had to give the math course at the community college my undivided attention, because getting a C- or D+ wasn't going to cut it. (Your Grade Point Average, the average of all the grades you've gotten, means little in American high school other than honors. But for getting accepted to college and meeting the requirements set forth by your diploma, it's VERY important. The bar isn't terribly high in most disciplines, but if you fail to meet the requirements, you ain't graduating. Nor can you continue to enroll in the courses you need to graduate, until you raise your GPA back up.)
And yes, doing too much CC can give you a false expectation of how difficult a 4-year university can be. Each class at a 4-year university beyond the 100 level courses tends to act as though you have no other responsibilities (even though your professors are aware you have TONS of other things to do.) So they will pile on to the degree the professor thinks is warranted, and sometimes, that can be a very nasty shock. Like I said above, CC's are generally focused on getting people through the curriculum and the overall workload and the depth of the curriculum usually reflects that. Universities aren't quite so forgiving, nor are they as concerned with your absolute success.