That was my take away from it. I don't remember what class I was taking or who the instructor was, but I remember him saying that, "Practice doesn't make perfect, it makes permanent!" He was warning us against learning something wrong. I was wondering if you instructors have to spend more time helping people unlearn bad techniques than simply teaching good ones.
It is often difficult to break a bad habit and instill a correct one in a shooter. I often like people to be very deliberate (I don't like to say slow) in their manipulations / actions so that they execute correct repetitions. Often people will want to increase speeds and "outrun their headlights" so to speak and execution goes into the toilet. I generally comment to them that "if you are fast and all fucked up, you're just teaching yourself to be fucked up very quickly".