One thing that I hadn't fully realized until I was about 30 or so: Your grades and test scores only matter to "the first". That is, your high-school grades and SAT scores only matter to the first college that you enroll in. After about a year or two in college, if you transfer to a different college, they don't care a whit what your high-school grades were. They want to know what your college grades are.

Similarly, your college grades and the name of the college only matters to your first employer. After that, future employers don't care what your college GPA was. They want to know what you've accomplished professionally.

This is not to say you can just slack your way through school. What it does mean, though, is that you shouldn't obsess about your GPA. Channel that academic energy into some actual achievements - not into ultimately meaningless points. In the end, accomplishments are worth much more than grades.