If you are in high school or college, you know that you will not get the best grades if you have bad study habits. Unless you are a naturally gifted student, it takes some effort to get the grade point average you need to continue in your academic career. Even if you are gifted, bad habits can hurt your scores.
Of course, the worst of the bad habits of studying is not studying at all. Some people plan to go through school without cracking open a book. It is rare for this to be an adequate response to academia. Most people need to study.