What Corbyn said + Samphire's very good-humoured anecdote.
Chill.
The question, for me, is this: Why is it getting to you?
I'm interested. I'm not shouting at you, or telling you you're a bad person. It's clear it has upset you - do you want to talk about/think about why?
You see, if that happened to me, my response would be determined by so many things. Mostly, my relationship with my children's teachers is so remote that I would barely register that - I'd forget it within half an hour, or even less. I have other stuff going on that takes more attention.
But, if it hit a nerve, or if it was based in some deeper situation, or if I'd thought I had a really great relationship with that teacher (some of my children's teachers I have really liked, and I do hope it was reciprocated) and was a bit hurt to find out they thought less than well of me, or if my self-esteem was a bit wobbly generally - then I might dwell on it.
Confession: I have done the 'telephone not properly put down/email sent to the wrong person' thing. And it is horrendous. And you have to grovel - grovel, grovel, grovel - over what was, really, a throwaway comment but has been turned into incontrovertible stone. It's so, so awful. So I really, really cut people slack over stuff like this.