As a writer, or an aspiring one, it's a good thing to have some sense of grammatical continuity, like commas, periods, not ending sentences with prepositions, spelling, etc.
Frankly, I have an overactive "edit check" permanently fixed in my head, thanks to my junior high English teacher, Mrs. Peters.
My impression of Mrs. Peters, to this day, is a no-nonsense type of person who holds every one of her students to the same standard, regardless of whether they're willing to live up to it. She enforced discipline in her classroom, endured complaining and whining from all of us, and drilled they're/their/there corrections and appropriate comma usage into our brains like a well-oiled machine. Every time I'm typing and I use the wrong it's/its, I cringe at the thought of what Mrs. Peters would say if she knew.
Thank God for Mrs. Peters.
Because of her, I became a marathon research essayist in college. Because of her, I flourish in the technical writing tasks I'm assigned in my current job. Because of her, I can appreciate literary devices and identify themes. Because of her, I can read and re-read my fiction and be proud that while I have not yet found my writer's voice, I have impeccable mechanics. And because of her, I can help others, like my husband, in their writing, and they trust that I know what I'm doing.
Every time I'm asked, "Who was the most influential teacher in your life," I'll bet you can guess my answer. :)