Regardless of Any Reason

Today, my teacher handed out paper for grammar activity. We needed to identify appropriate part of speech for each words. There were ten sentences on this paper. I thought that's very easy, and I finished within 2 minutes. When I finished it, I wanted to make sure my answers with my classmates. However, they were still doing on second sentences. I was surprised most of students were not able to do well. They were really confused. My class is advanced class, and I thought that was not advanced activity. While many students just started learning English from advanced level, I started taking a beginning class three years ago. I have been studying very seriously since then. I thought all my hard effort was not waste of time. When I started learning English, my ESL teacher said, "All students, who just started learning English when they are adult, need to keep learning English seriously for at least 15 years until you can use it well. I'm sorry, but it's true."  I was really shocked because I felt like learning English is endless. However, I can understand it now. We need to keep learning seriously. Regardless of any reason, the most important thing is that we shouldn't stop studying.