If you can imagine that you are like a spinning top and if someone or something attacks you, they will fly off from you and not be able to enter into your body. In Aikido all movements must be 'circular' - not 'triangular'. Thus if you are spinning like a top and your opponent is on the outside, he is controlled not by strength but by your movement. At the same time your body and mind must be relaxed. We then have a posture which is completely alert.