Cognitive dissonance is the term used when a person holds two contradicting beliefs or thoughts. And the normal human psychology is to alter this cognition so that the person thinks the final outcome was in his favor although in reality the opposite might be true.
In the fable The Fox and the Grapes by Aesop ( 620–564 BC),a fox sees some high-hanging grapes and wishes to eat them. When the fox is unable to think of a way to reach them, he decides that the grapes are probably not worth eating, with the justification the grapes probably are not ripe or that they are sour.
The above story clearly depicts the normal human behavior. At the beginning when we set our goals very high and tend to work for it. Sooner or latter we realize that its a very tedious job to reach that goal. Then comes the concept of shifting the goalposts which suits us - and more precisely the lazy mindset which has taken a front seat by then.
The road to success lies in addressing this problem of cognitive dissonance. Rather than justifying the failure to reach our goals and stopping the efforts, it is advisable to learn from the setbacks and never move away from achieving the goals.