When you are playing music it is important to be healthy about your movements and technique. If you are not healthy and careful then you will find yourself hurting and no one would want that. Remember that your fingers work because your brain sends signals through your nerves so that they work properly. Your nerves stay healthy because they can send signals freely. If you block the path by continually, abnormally bending your wrist, your nerves will start to throb. Do it long enough to cause damage and you get something called carpal tunnel syndrome. And if it is bad enough you may need surgery to fix it and get the pain to go away. We don't want that! So, to avoid this injury, keep your wrists relaxed but straight so that you are not creating any kinks in the nerves inside the tunnel.