Kishaba Sensei said that good karate has 3 elements: Speed, Power and Grace.
I try to keep these elements in mind every time I do a kata or a waza.
One of the things that helps enable these 3 elements is natural movement.
Shorin Ryu karate has a strong focus on natural stances and natural movement. We spend much of the time in our kata in natural stance. Foot placement in our stances is much narrower than other styles. When we step, it's a natural step, not a "c" step. Even moving from a high (natural) stance to a low (front) stance, the movement should be natural.
In order to have natural movement it is important to find the connection between the lower and upper parts of your body. If you move the lower parts with different timings than the upper parts, movement is not natural. Only when you can find a balanced connection between the upper and lower parts will you have natural movement in your karate.
Of course, natural movement is easy in the things we have done our whole lives. Activities such as walking, running, writing, eating--these are all very natural things. They are so easy, we rarely have to think about them to do them.
In order to obtain natural movement in karate, we look to the kata we practice. The kata allow us to train our stances to be natural, to train the movements of our arms to be natural, and to train the connection between our lower and upper parts of our bodies to be natural.
Through repetition and introspective practice of kata we can obtain natural movement in our karate.