On the morning of my wedding, the third time I'd met my soon to be mother in law, I was understandably jittery about the day. Probably not at the top of my game.
So, I warmly greeted her by saying "Hi Linda! It's so good to see you!" She's quiet for a moment, and then says "Actually, it's Laura." I knew it was Laura. I have no clue why I called her Linda. I was mortified, and felt like I had only one way out of the situation. I replied after a pause, "No.. I'm pretty sure it's Linda.".
To her credit, and to this day, whenever she calls me she tells me it's Linda, and I've never called her anything but that since.