Good work Famine...
First, you're not truly "free" yet. I personally found that, while graduating high school was great for me at the time, turning 21 actually was my truest moment of freedom. The day I realized the world was a pretty wide open place.
You've got 3 years of a goofy "limbo" to go through, but it's a hell of a lot better than the years in high school.

Second, make sure you enjoy your college years and don't goof off. Have fun during them, but make your best effort too. You'll appreciate the growth later.
And third, don't drink too much and develope a horrendous beer gut. It's a very common side-effect of graduating high school that can take upwards of 12 years to develope, but it can happen!