A story by the Buddha to illustrate habituation and the resulting closed-mindedness:
“A young widower, who loved his five year old son very much, was away on business when bandits came who burned down the whole village and took his son away. When the man returned, he saw the ruins and panicked.
The took the burnt corpse of an infant to be his son and cried uncontrollably. He organised a cremation ceremony, collected the ashes and put them in a beautiful little bag which he always kept with him.
Soon afterwards, his real son escaped from the bandits and found his way home. He arrived at his father’s new cottage at midnight and knocked at the door. The father, still grieving asked: “Who is it?” The child answered, it is me papa, open the door!” But in his agitated state of mind, convinced his son was dead, the father thought that some young boy was making fun of him. He shouted: “Go away” and continued to cry. After some time, the child left. Father and son never saw each other again.”
After this story, the Buddha said: “Sometime, somewhere, you take something to be the truth. If you cling to it so much, even when the truth comes in person and knocks on your door, you will not open it.”
Read more at Source: Introduction to Emotions