Do you remember sitting through those dreadful grammar classes? I sure do. I remember being asked to memorize the function of a noun, pronoun, verb, adverb and adjective. And I remember learning the difference between the subject of the sentence and the predicate of that same sentence. I have no real memory of how the concepts of grammar made it off the pages and from the teachers' mouths into my head, but they did. I never intentionally paid attention during grammar class because at that time I was years away from deciding to be a writer. I guess the grammar I needed to learn somehow came to be through osmosis. Think about our what our society would be like without the existence of grammar.
Basically, grammar is the thing that allows us to communicate the same kind of English. Sure, you and I both know what a dog or a tomato are, but what if you thought that each sentence that ended with a period was really a question. Wouldn't that be confusing? Or what if I decided to write my next novel uses sentences like this: "Told Billy to Sarah loving a mother being a." Does that make sense to you? Of course not, because that sentence was not written with proper English grammar in mind. If we're lucky or just have a good imagination then we can determine that Sarah is telling Billy something about loving to be a mom. But without grammar, understanding even the most common English words just isn't easy.
Do you love to sit down and read a good book? Or perhaps relaxing in front of a movie is your cup of tea? Do you enjoy surfing the internet for the latest facts and news? If you enjoy any of these things, then you better appreciate grammar. It is proper grammar that allows you to read a book or to understand the script of a film or even to make sense of the internet.
If you still are not convinced about the importance of grammar to your life, trying having a conversation using mixed up sentences like the one I wrote for you earlier. It is pretty hard to make it through a day when no one understands each others thoughts or questions.
Fortunately, because we have grammar, we never have to worry about miscommunicating with people because of the way we arrange our words. So be thankful for grammar because I guarentee it has made your life a lot easier.