Did you take the PSAT this past year? You'll do even better on the SAT. Do you know what you want to study in college, versus just wanting to go? That could help with your excitement getting there and looking forward, thus seeing the testing, essay writing, etc. as chores/assignments that have to be done like any other.

College was a bit of a letdown for me; high school was actually "harder". I got my first degree mostly on my native intelligence and what I'd learned in high school. If you enjoy specific subjects that can help and if you have good study habits. I would drop some of the care about grades; when you graduate from college, no one will care and when you get into college, no one will care what you did in high school, etc. Getting into college pretty much happens with your freshman through first semester senior grades anyway since you have to apply and get accepted before you graduate. With your grades, I'd apply for early admission or other sorts of things, just for the practice. See if you can think of the application process as a "game"/maze. Back in my day (pre-computers) we had to go to the field house and stand in lines to register for classes and I use to time myself each semester, to see how fast and well I could get through (can be hard to get certain popular classes or professors).