Winston Churchill's secretary once circled a sentence on a manuscript she was proofreading for him, because he had ended a sentence with a preposition.
He wrote back, "This is exactly the sort of thing up with which I will not put."
The point being, grammar rules should not get in the way of effective communication.
In my world, grammar is flexible depending on the context, the audience, the purpose, etc. On the other hand, spelling errors and pronunciation errors drive me insane!