What advice would you give a high school slacker before he went to college.

I graduated high school last may and had almost no intention of going to college. I never fully ruled it out but it wasn't "part of the plan."

I have now decided that I want to join the ROTC and although I'm still not keen on the thought of going to college, I've decided it will be worth it. While I'm there, I may as well study criminal justice.

But on to my main concern: I was a big time slacker in high school. I failed exactly as many classes as I could and still graduate. Although my attitude has changed in the last year or so, I'm still worried that I won't be motivated enough and I know that laziness really won't fly in college the same way it did in high school.

So.... any nuggets of wisdom?

TL;DR I'm pretty lazy and going to college; is this as big of a problem as I think it is and what can I do to remedy the situation?