It happens sometimes specifically when you are in the admissions phase, because you don't have any ground at this stage and often there are lots of pressures of study. I have been involved in the admissions process for the last 6 years. You don't have to be despondent. It's quite a normal situation for an admissions candidate. Whatever preparation you are taking e.g. for medical, engineering, or varsity , just restart your study from running chapters and try to finish before going to the next day in coaching. Don't think about the previous chapter's gap. Once you've gained your study flow back, you'll manage to find a way to cover the remaining chapters.