One of the things that really bothers me about political discourse is when someone, anyone, gets criticized for changing their mind.
When you have evidence that something is/was wrong, or that something else has a good probability of working better, then you SHOULD change your mind.
I recently went to a talk where the speaker laid out the research about the effects of correcting grammar in student papers. According to the research (and I trust that the speaker did a good job looking at all the research), it does no good (and may do harm) for an instructor to mark or correct grammar in student papers. The research looked at lots of different strategies: code and look it up, check and have the student correct it, and on and on. And none of it, NONE OF IT, actually worked to get students to write better or more grammatically. None of it.
In the face of that evidence, I'm going to do my best to stop marking grammar and proofreading sorts of stuff, and focus my energies more on responding to ideas and big picture stuff. I expect that to be hard, because I've spent a lot of time doing grammar and proofreading marking. But that's going to be a focus for me this semester.
In other words, given a good deal of evidence, I've changed my mind about my teaching practice, and will be trying to change my practice.
I think that's healthy. I also think it's healthy when politicians change their minds. Evidence shows that glbt folks aren't dangerous to have in the military? End Don't Ask/Don't Tell. Evidence shows that there aren't actually weapons of mass destruction in Iraq, change your mind!
Mostly, I want students to really think about how they "know" what they know, and to be willing to change their minds in the face of good evidence to the contrary.
What have you changed your mind about?