We can see that, when our right hand takes hold of something, the left hand wants to help it. When our right foot goes out, the left foot at once wishes to join it. When we fold one arm, the other arm wants to be folded too. One leg inclines to cross the other. In India there is a superstition that it brings bad luck to sleep with the legs crossed. Everyone knows it, but it is most difficult for anyone to get out of this habit because it is so natural.