A Zen master was making a painting, and he had his chief disciple sit by his side to tell him when the painting was perfect. The disciple was worried and the master was also worried, because the disciple had never seen the master do anything imperfect. But that day things started going wrong. The master tried, and the more he tried, the more it was a mess. 

The master tried and tried and the more he tried - he started perspiring. And the disciple was sitting there and shaking his head again and again negatively: 'No, this is not perfect.' And more and more mistakes were being made by the master.

Then the ink was running out so the master said, "You go out and prepare more ink." While the disciple was outside preparing the ink, the master did his masterpiece. When he came in he said, "Master, but this is perfect! What happened?" The master laughed; he said, "I became aware of one thing: your presence. The very idea that somebody is there to appreciate or to condemn, to say no or yes, disturbed my inner tranquility. Now I will never be disturbed. I have come to know that I was trying to make it perfect and that was the only reason for its not being perfect."