Knowing When It's Time To Quit & When To Stick It Out?

I'm taking a c++ course because I really want to get a degree in computer science. However, I am not a person that is good at math and I tend to make a lot of small mistakes. This week I have my final in my very first c++ course (Intro to C++). I failed the last test. It took me literally 3 full days to do an assignment on functions. I read and re-read the chapter on functions, read articles online, read and re-read my notes and functions finally clicked. My question, however, is it really took me a very long time to understand functions and I know the courses will only get more difficult. I want to be realistic about the things I can achieve. Is it time to switch majors because maybe C++ is just too much for my itty bitty brain to grasp? haha. Seriously, though. Am I just being a quitter or am I being realistic?