well, actually, grammar rules themselves don't exist. there has never been any set rules, because the "rules" depend on how a majority decides to speak, and they change as the years go by. "ain't" used to be considered grammatically correct and was used by rich English folk, but when "commoners" started using it, they decided it wasn't proper English. this fact won't change how society treats grammar (like it's friggin LAW), but I feel like we should all be more lax and just use whatever feels right to us. I mean, soon, "I did good on my test" will be considered proper grammar.