Fellow nursing students/nurses...

So I am starting prenursing courses in the spring and I can't help to feel scared yet excited. The 3 classes in my schools program for prenursjng are pharmacothereutics, pathophysiology, and foundations or nursing practice. What can I expect from these courses?? What are they mainly about etc. Also, was nursing school really as hard as everyone claims? I'm scared I'm going to fail :( and I have only gotten 1 B grade. I want to go to grad school so I need to maintain a good GPA. Advice, and opinions greatly appreciated :)