I wish I could say that there was a teacher that helped change my self-image, but really no one comes to mind. There were a number of teachers I liked, and those who helped form me, but there wasn't one that really initiated change.
I think it's important to note that some teachers can negatively impact people, too. There was the one teacher that told me I needed to do better because, after I'd moved to the suburbs from the inner-city, I was "with a lot of smart kids now." And the one who willfully looked the other way as I was bullied mercilessly. And don't get me started on my mother!