The fact that you have this aspiration is my first clue to the degree of motivation that you already possess. Secondly, you appear to be a student that is willing to sacrifice and do not only what is required,but go above and beyond. I do have several suggestions, however, that you might try to reduce your frustration and increase your overall success as a student. I suggest that you review your study methods and consider changing your study behaviors. If for example, you simply read and reread notes and text, you may not be retaining enough of the material.
Study skills are like a bag of tricks or anarsenal against difficult material.
Do a keyword search for study skills on the Internet and see if you can add to your study skills arsenal. Motivation is a characteristic that so many desire and so few are able to maintain for long durations. Those that are highly motivated are rewarded generously. I encourage you to read the biographies of people like Donald Trump, Lee Iacocca, Mario Cuomo, or others to get a perspective on these qualities and others. As I write those names, I realize you may not know any of these outstanding individuals, so pick people who you feel are leaders or successful individuals and read about them.