I'm not suggesting you accept poor grammar from yourselves but you should give yourselves a break. Watch any North American tv show that includes real people, average folks speaking without a script, and you'll quickly realize that proper grammar is a rarity rather than the norm. Quite often I hear English that hurts my head trying to understand why they are phrasing things the way they are, and trying to decipher the actual meaning.
And writing skills are equally dismal. The whole "there they're their" issue is just the tip of the iceberg. As I learn Spanish I am constantly confronted with basic issues like bien vs bueno, things that average English speakers have no clue about in their native language. It makes me see that these details are important for a language learner but you certainly won't stand out as an idiot if you don't master them.
So take heart & work towards improving yourself but realize that you're probably aware of more language/grammar/spelling issues than the average English speaker.
I was recently in an interview panel for a job here at my work. Part of the interview process was a short written memo or e-mail regarding a subject common to the job. All the candidates were native speakers of English. Of the 5 candidates, only one wrote something that was at all close to acceptable. In fact, I regularly see writings here from English learners, along with apologies and requests to correct the text, that are written better than what I saw that day.
So I absolutely agree with Dave. We should all hold ourselves to a high standard and try to achieve excellence in our target languages, but don't be too critical of yourselves along the way. You are probably doing better than you think.