A guy that I teach TKD with says this a lot. He's full of crap most of the time (you know the type, always right, always has a better story, no one else's ideas are as good, always wants to look smart and important...)

Most of the time his ideas are to be taken with a grain of salt, but I agree with him on this one. I've expressed this idea to the kids we work with from something I learned as a musician..."If you can't play it (do it) slow, you can't play it fast".

The kids, when learning a new technique always want to do it fast right away, without learning the mechanics, and they always do it wrong and someone usually gets hurt at least a little.

Point being...good advice Xavier.