One of the speaking rules you need to know might sound strange to most ESL (English as a second language) students, but it is one of the most important rules. If you want to pass examinations, then study grammar. However, if you want to become fluent in English, then you should try to learn English without studying the grammar. Studying grammar will only slow you down and confuse you. You will think about the rules when creating sentences instead of naturally saying a sentence like a native. Remember that only a small part of English speakers know more than 20% of all the grammar rules. Many ESL students know more grammar than native speakers. I can confidently say this with experience. I am a native English speaker, majored in English Literature, and have been teaching English for more than 10 years. However, many of my students know more details about English grammar than I do. When they sometimes ask me about grammar, I can easily look up the definition  and apply it, but I can't tell them the answer _  I often ask my native English friends some grammar questions, and only a few of them know the correct answer. However, they are fluent in English and can read, speak, listen, and communicate effectively. Do you want to be able to recite the definition of a causative verb, or do you want to be able to speak English fluently? According to the author, what opinion do most ESL students hold?
Grammar matters a lot only in speaking. Grammar doesn't matter much in speaking. Grammar is very important in English learning. Grammar is not important in English learning.