A little late I know, but my attempts to post this from my phone while sitting in a slightly damp and very cold tent were a bit of a failure.
Speaking of failures...
Not strictly a teaching failure, but the one that I still shudder to think about took place during a parents evening during my second year of teaching. I don't really remember the details, but at the end of a five minute conversation with a mother and her daughter, during which I had used (what I thought was) the girl's name on several occasions, the mother leaned in and said something along the lines of 'you know that this is <insert different name here> right?'.
Between silent prayers for the earth to open up and swallow me whole I think I mumbled an apology, assured her that the comments were all still relevant, apologised some more and wondered if a complaint would follow.
From then on, I've always made sure I've been doubly sure of the names of my students!
Image credit: en.wikipedia.org/wiki/Name_tag