The recalculation date is intended to help students receive financial aid funds for courses that don't start at the beginning of the term, or that are added after the first financial aid check has been disbursed.  The recalculation date goes both ways, though.  If you drop units, you also may have to repay some or all of your financial aid.  Therefore, from a financial aid perspective, it is always better to remain in all of your classes until the end of the semester.  If you are struggling, seek help from one of the many tutoring resources available on campus and meet with a Counselor to discuss all of your options and the related implications.