I did karate for a little while when I was a kid. In my Muay Thai class, I was told I am putting too much foot in to my kick. They explained I need to bring my knee up higher, allow my hips to do the power, and leave my leg and foot limp and just swing it around. I had a hard time doing this, as it felt really un-natural. Any drills I can do at home to help me improve?