Bad at Grammar

Today, I studied English grammar in Susan's blog. I have been believing my grammar was good, but my reality was not like that. I solved some quizzes about prepositions: at, in and on. At first, I was confidence at those quizzes. During doing the quizzes, I made a lot of mistake. As time passes, there were same quizzes. But I was confused. As a result, I solved the answers just 60% correctly. From this, I made a decision to study grammar in enthusiasm. I will study grammar 1 hour of a day.