I agree, you should do all of those things, especially since with math-based subjects how well you understand the later material greatly depends on your understanding of of the earlier material. You shouldn't fret though. You can still easily pass the course with a high grade, and many professors will throw out your lowest test if score higher on the final.And as for bad grades, I once had turn in a blank test!

If you're not doing quantam mechanics, feel free ask me...