On a cold winter's day, some porcupines huddled together
to protect themselves from the cold. Soon, however, they were too close together and began to prick each other with their quills.
The pain forced them to move apart. When the need to keep warm brought them back together again, the same thing happened, over and over again, until they found the right distance that allowed them to keep each other warm without hurting each other.
(Arthur Schopenhauer)