This will depend on how strongly your sense of self-discipline is! If you have gone through sports, music, drama, debate, etc. - things requiring a lot of sacrifice to get to where you want to be, AND, you did it pretty much without parental nagging to get you there, then, you should do fine! On the other hand, if you get to college, and go, "wow, I'm free!" you will be in trouble.
Along with that self-discipline will go the need to eat, sleep, and exercise properly, AND learn to give yourself breaks. If you try to constantly be working or studying, you will burn out. You deserve some "me" time!
Also, I want to encourage you, on the first day of class, to ask your professors "how" they test. There is nothing worse than having a midterm that covers five chapters and lots of lecture notes, and studying ALL of it, only to learn that NONE of it came from the books! (that's what I did!) You have only so much time. Don't study stuff you don't need to study!
While work study can be pretty laid back, remember, it is a job, and you should treat it as such. You want to be able to use them as a reference when applying for future jobs.
Best of luck!
+ Organize your day and studying
+ Keep a detailed calendar/schedule
+ Proactively communicate with your work/study supervisor, and let them know when you might need time off to study for finals, complete a major project or paper, etc.
+ Prioritize your classes, then your job; limit extra-curricular activities and clubs, particularly during your first year.