Whether we need a teacher or not depends on circumstances. The relationship with your teacher and a new subject is somewhat similar to that between a tour guide and an unknown city.
When we come to an unknown city for the first time, we definitely need a tour guide. We might have a detailed map, but it is unlikely functional-it is not surprised that we can hardly interpret those mysterious symbols. Likewise, when we are beginner, it is wise to learn with teachers. They can tell us where to begin with, what we should do, and which reference we should choose. When we confront difficulties, we can ask them for help, and their advices will always be tremendously helpful. With teachers' assistance, we might learn easier, faster, and more interestingly.
After a period of time, we have learned a lot. We now know the city pretty well, even though there are still many places we haven't been to. It doesn't matter. Now that we are able to recognize those mysterious symbols on the map, what we need perhaps is not a tour guide but a more detailed map. Similarly, we need richer references for learning. Yes, there are still many fields unexplored; they are, nevertheless, no longer puzzling. The task is simple: we will explore them one by one, little by little. If we are working on a certain skill, practice more; if we are preparing a test, practice more; whatever we are learning, what is always to bear in mind is that, like people always say, practice makes perfect.
After another period of time, we might have become others' tour guide, but we still want to make out more. We want to know which restaurant is the most decent, which bookstore is the most professional, which coffee shop is the most classical. Even the most comprehensive map doesn't have adequate information. We again need experts. In