Cause and effect

My mom often said that:" You'll fail you class if you do not study hard!!!".But I think my mom's idea was wrong becauce there are three different reasons to fail a class. Bad study habit is an important reason at first. If we want to be success in our class, we need to set up our timetable and follow our schedule. We should be not study and watch TV at the same time because it is very hard for us to concentrate to our lesson. Moverover, going out with our friends is another reason and my friend was an example. He always went out with his friends every single night,so he often came home late and he did not have enough sleep. That was the reason why he had no time to do and prepare carefully for his class. In the end of quater he failed two of three class that he had taken. The class reason is that we do not have any goal for my life. In my opion, we should have a plant for our life in the future such as what a job we want to be. In my case, I want to be a doctor so I need to study hard in my career if I want my dream to be come true. And I think we will be sucess in our education if we know clearly about the reasons that make we fail.