My worst school years were when I did not keep up because I didn't care for the subject. Get over it. If the course is required you have to take it and do well. Putting off studying and keeping up with the curriculum will only make getting ready for tests more difficult and you will not have as good understand of the subject. This can rub off on other subjects as well while you cram for exams.
The semesters I got a jump on all subjects, especially the ones I did not think I would like, I did much better. Whether it was by reading text book ahead, ready to ask questions in class or understand the lecture and making sure my class notes were well done and I reviewed them after class to fill in gaps, it all helps build the foundation for the subject matter. Generally if I did this, by the time the semester was 60% complete, the remainder was a breeze. Made all the difference for me.