When I was younger, I had much longer hair than I do now. While doing some experimentation on a spell, two of the ingredients reacted in a way that I ought to have expected, but I simply hadn't been paying close enough attention to realize what I had done. Anyway, it caused a slight explosion in my lab. Though I was lucky in that my general injuries were minor and treatable with some clerical assistance, my hair was not and I have kept it short ever since. It is both a preventative measure and a kind reminder of my hubris.