Grammar Errors, Grammar Errors Everywhere

I don't know why I keep making grammatical errors while writing and also while teaching.... err.. sometimes, but while teaching, it is more terminological mistakes. I need to study grammar again. Since working here, I can never have time to study grammar (to do the exercise). Now, I have to mark English test papers so it makes me feel more bad. I used to have the terms like the back of my hand. Urggghhh... this is very bad. I feel dumb. Blergghh.

P/s : I miss teaching. I mean real teaching, and not coaching. I'm not a coach, I'm a teacher! :(