My wife teaches English at the local university. Sees too many people with great promise mess themselves up. So humour me...
Party, have a blast etc. ... it can be the best of social times. But don't forget why you're there. This is not like high school ... there's nobody there to keep you on track except yourself. For lots of folks, this is their first time being fully responsible for themselves ... and they have some pretty big hiccups at the start. It's common to spend December's grocery money on October's boy's night out ... don't.
The work will be different, and more challenging than you expect. More of it too. Don't let it faze you - you can handle it just fine. It also gets more interesting the further you go. In 1st year, you'll take a huge range of things ... in later years, you get to concentrate on what really turns your crank.
If you're like most people, your grades will be lower in first year than they were in high school, at least at the start. As you sort out what's expected, and focus on what you find you're best suited for, they'll recover. There are some ways to jump ahead on this learning curve ...
Obviously, don't short-change the time your work really requires. It will take longer than your estimates, and you may need to find somewhere other than your room to work. But more important, you'll need to change how you think about learning. You're a participant now in working this stuff out, not just a scribe writing down someone else's ideas. The most important question to ask is "so what?" Why should we care about all those facts ... what do they mean ... what are the implications? Just writing down your Prof's words won't get you above a C, if that. History isn't just history, it's a record of how people have thought and reacted under pressure ... Works of literature aren't just stories ... they're the dreams and nightmares of the age when they were written. Economics isn't just about money ... it's set of theories about how folks see value ...
You're going to have a grand time. But you're paying for this, right? Make sure you walk out with everything you paid for. I've met a few folks who wish they'd partied more in college ... but lots more who wish they'd really milked their college years for everything they could.
Tom.