I was in a similar situation as you, 4 years ago. I worked a fair bit harder, learned WAY more, and had a WAY better time in college. To be fair, my work ethic is still not very good, but I pretty much get A's in the classes I care about and B's in the ones I don't.

I suspect that you will be fine - you're probably smart enough that college won't be as hard as you might think, and you'll also be more motivated to dig up good work habits if you really need/want to.