The biggest thing I am seeing CPs learning (at least the smart ones...) is a work ethic. Your job is important or they wouldn't hire you to do it. I also think it's important to remember that you have taken someone else's opportunity, so you need to respect that and do the very best you can do in your job, whether you wind up liking it or not.
Before you arrive, you should know that it is a JOB and it is WORK. It is not meant to be fun playtime and ooh, let's party. It's not like college where you can slack off until the last minute, then whip out a paper and still pass the class or make up some excuse for the professor and have them be a pushover. You will work hard, sometimes long hours and deal with sometimes less than magical situations. The payback is, there is a TREMENDOUS amount to learn if you show up to work, pay attention, and listen. Take advantage of the classes and find ways to maximize your own experience by doing things here that you can't do anywhere else. I know too many people who sleep or party all the time rather than take advantage of the opportunities here and they will be the ones who go home and complain about how awful it was.