Kathy Willens, Associated Press photos
As an example in a simple form, think of how many baseball spectators will bias their perceptions by personal wishes for a particular outcome. Often it isn't based on an accurate judgment of what has happened but simply a desire to have things 'go their way'. If truth happens to coincide with sentiment, then all is well. If not, the call at the plate can be blinding.
It is prevalent in human nature and I am, at times, a part of this. I might consider every failure I've ever experienced and simply claim that it wasn't me, but that just isn't so. I hope to recognize this weakness often and know that I am a responsible player in my life.