Quote Denis DNT
How often should we Jenny? That's the point?
Well, I have apologized. But it's embarrassing, isn't it? I'm sure you agree that we desire to teach what is right. The times I have had to apologize have sent me back to the books to make as sure as possible I didn't have to do it very often!
I always tell my students, "Don't look at me as a walking dictionary. You are not one yourself for your native language." This has helped reduce potential embarrassing moments for me.