During the time of Mahabharata, Guru Dronacharaya used to teach Pandavas and Kauravas. One day, he decided to test the caliber of some of his disciples.
He called Duryodhana to his chamber and asked, "Son, go, find out a good person and bring him to me."
Duyodhana replied, "OK sir, I will go in search of such a person right away."
He came back after some days and told Dronacharaya, "Sir, I have carefully searched many places far and wide but, unfortunately, I couldn't find a good person, whom I could bring to you."
Listening to him, he asked Duryodhana, "OK, send Yudhishtra to me."
Yudhishtra came to Dronocharaya, who asked him, "Son, go, find out a bad person and bring him to me."
He agreed to obey his order and started in search of a bad person. After many days, Yudhishtra also came back empty-handed since he couldn't find a bad person, whom he could bring to Dronacharaya.
Dronacharya asked him, "Son, you have searched many distant places. Still you couldn't find a single bad person."
Yudhishtra answered, "Sir, though I did find something bad in many but didn't find something really bad in someone, whom I could bring to you."
Other pupils were surprised at his answer and asked Dronacharaya, "Sir, how is it possible that Duryodhana couldn't find a single good person whereas Yudhishtra couldn't find a single bad person?"
Then Dronacharaya explained to them, "Dear disciples, we judge a person from our viewpoint if one is bad or good. Yudhishtra couldn't find a bad person as he is himself good. It's only a matter of our viewpoints. But always remember that our viewpoints tell everything about us too."