Anything C and above is a reasonable grade in my opinion. C is average, B is very good and A is excellent. I've always been an average grade student, and I'll self confess that it's probably because I don't work to my full potential. But I'm the type of person who is happy with a pass. A grade C or above. While it's nice to work harder and achieve the higher grades, the world is not going to end if I get a C.
The good thing about higher education (university) is that you are not graded on the A/B/C/D scale. At least, not at my university. That kind of takes the pressure off.