ctuma2,
You can't change what has already happened. Look at what you can correct and improve yourself for down-the-road.
I'd recommend you work your tail off for the next two semesters before a transcript is mailed off. You have plenty of time to prove yourself. One grade of a C from your sophomore year on isn't going to be a tragedy.
As much as USNA (can't speak for other SA's, but probably assume they do the same) looks at GPA, they also look at rigor -- that is what were the grades in the challenging (Honors, AP/IB) or non-challenging courses you earned.
Also, as I mentioned in a previous post, if you are shooting for A's and B's (which you should be shooting for), then get help from your teacher as soon as you have the slightest indication your falling behind (either homework, quiz, test) and make sure you understand how to improve yourself. This does two things, one, helps you get better grades and two, normally gives the teacher more discretion in grading based on your "outside the classroom" efforts.