First off, stop worrying about making mistakes. There will be plenty of other things to worry about. Mistakes are going to happen, whether you're worrying about them or not, so what's more important is recovering from them quickly and learning not to make that particular mistake again.
I was nervous for almost my entire senior year, but toward May and June I started looking forward to college. I started to look forward to getting away from my family for long periods of time. (my brother, at the time, was a huge annoyance ) And fortunately I adjusted to my new life rather quickly.
And you don't really have to think about it as living "alone," because more than likely you're going to have roommates/hall-mates/apartment-mates and you'll meet people who have the same interests as you. Might take a while (It did for me), but you'll find the things you're worrying about now aren't so bad.
That's not to say there's not a lot of stress involved. Feeding yourself, keeping yourself motivated, doing all those papers and projects, paying your own way, etc. But you'd be surprised how easy it all becomes after a while.