This is a story I heard a long time ago...

There once was a walled city which had two gates.  At each gate sat a beggar who would greet the new visitors and hope to be rewarded with alms.  One beggar would say how the visitor should be careful of all the people in the city.  Most were evil and mean spirited.  So the visitor would find lots of mean spirited people wherever they went.

The other gate had a beggar who would tell the visitors how good and kind the people in the city were.  And the visitor would be amazed at the kindness and goodness of the people. 

 Point is if you look for the goodness in people you will find it.  And if you look for the evil it is there too.  The people were the same ones just the perspective was different.