Fast is a four-letter word
My biggest problem in Iaido is I don't slow down enough. I go too quickly. If you go too quickly it throws off your balance, it throws everything off, and you don't internalise the waza so that when you're a 70-year-old 8th dan, you can make it all look as smooth as butter. While I was on my own doing a little work on Kesa-giri today, sensei was making some commentary to another student about their work with the same waza, and then he said, of me, "She's a completely different person when she slows down." I take that as a compliment.