What do you see here?

One day the teacher called his disciples and showed them a sheet of blank paper, in the middle of which there was a fat black dot.
"What do you see here?" The teacher asked.
"Point," answered the first student.
"The black point," - confirmed the other.
"Fat black point," - said the third.
And then their beloved teacher cried.
"Tell us, what are you crying so bitterly about?" - the students were surprised.
"I cry that all my students saw only a black dot and no one noticed a big white sheet ..." the teacher replied.
How often do we judge a person only for his small shortcomings, forgetting about the merits!