We observe the small negative quality in others, but overlook the vast positive qualities in the same person. As the following anecdote goes:

Once in a seminar the speaker put a black dot with his marker on the white board. And he asked the audience what they all saw. All replied they saw the black dot. The speaker retorted, “Every one of you said you saw the small black dot in the centre. But no one said he/she saw the big white board.” In the same way, we see the negative quality in others first, however small it might be; but overlook, or fail to see the positive qualities in the same person, however immense they might be.