Occasionally something happens beyond your control, you do badly in a course, and you have to repeat it. More often repeating a course is part of a pattern of being inefficient. Mathematics cannot be acquired casually. You need to commit time and effort. If you can't do this don't take that course! You may feel that you should be able to learn mathematics on the side, with little effort, but like any worthwhile endeavor in life, it doesn't work that way. If you can't allocate the necessary time that doesn't mean that you are a failure or something is wrong with you, it just means that you are committed to other, no doubt very worthwhile, matters that at present rule out your study of mathematics. This may be unpleasant but that does not make it any less true.
Fine print, your comments, more links, Peter Alfeld, PA1UM