Think about it for a minute. Where did you learn grammar?
(pausing while you post your story in the comments.)
Me, I had a mother who corrected pretty much every sentence I ever uttered through grade 8. I also loved Mad Libs and parts of speech are pretty easy from there. In high school I had an English teacher who was a stickler for grammar as well. Diagramming sentences anyone? I have a love/hate relationship with them.
Now switch gears a bit. Where did you learn to write? Did those grammar lessons make you a good writer?
Good writing and good grammar are two different things. It's balance between the two that make it worthwhile. I can't ever read Angela's Ashes because of the complete lack of punctuation. It makes me want to pull out my red pen and edit away.
I like to think I'm a decent writer. But as far as a good grammarian? The jury is still out.