There grammar is worse

I just scared myself. I had written an e-mail and was reading it over before I sent it. To my horror I noticed the line "Next their going to say..." Ouch. Although I am an engineer, I take pride in having good grammar. I know the rules of the language, and try my best to follow them and to not split infinitives and such. Whenever I see someone blatantly destroying the language it bugs me. Now am I becoming one of them?

I have noticed myself mixing up the words that sound like "there" a couple other times in the last couple months. It scares me to think that maybe it has happened more than I have noticed. Maybe people are pointing at me and making fun of my grammar. I know the rules. Why am I suddenly screwing them up so much?

I am still proud to say that I seem to be staying legal with s's, apostrophes and plurals. Theirs no way I will mess those up.