Although examples of self-fulfilling prophecy can be found in ancient literature, the concept is credited to American sociologist Robert Merton, who defined it in his book Social Theory and Social Structure, published in 1949. Merton used the term to formalize the prophecy’s structure and consequences as he described how a statement or believe may alter actions and ultimately become true.
People who tend to be caught in negative self-fulfilling prophecies often suffer from low self-esteem where they act upon an overly critical self-evaluation. They tend to have a pessimistic view of the world and their chances to influence their own situation for the better. This leads to a vicious cycle, where their negative mindsets strengthen their self-fulfilling prophecies.
Most of us have experienced an important project at work and have to deliver a speech in front of co-workers or management to give a status report. You have diligently prepared, sought feedback from others, and you are ready to deliver on expectations.  
However, have you ever woke up the morning of the big event following a lousy night’s sleep and you suddenly think to yourself: “This is not going to go well.” This thought keeps rattling around in your head as you expect failure!
In situations where we act on the basis of an expectation, we may actually influence the outcome. When this is happening, we create the very conditions we actually believe exist or will happen. Even when we have done a great job and it’s time to reap the benefits and there is absolutely no need to worry, the feared-outcome may take place if we act as if there were some basis for the fear.
We have read the stories of experiments with children in classrooms. Although there may be no apparent differences, one group is told they are over achievers and the other group told they are average. At the end of the experiment the groups perform they way they are made to believe.
Now, it's important to realize that self-fulfilling prophecies are everyday experiences--not just laboratory experiments. What do we expect our day to be like when we get up in the morning? How much success do we expect for ourselves?
If we predict failure, failure is generally what we will find. If we expect excellence, excellence is very likely what we will get. How we think about a situation determines how we act, and how we act, more than anything else, determines the results.  
That is how self-fulfilling prophecies work. There's nothing magical about it. What we get in life is pretty much how we behave, coming back at us. To me, it makes perfect sense. 
Do yourself a favor this week, and see if you recognize areas where you are setting yourself up because of your expectations. If you are setting yourself up for the good, terrific! If not, what can you do to change those internal expectations? Replace the negative self-talk with positive self-talk. Consistent doses of positive self-talk will change how to relate to yourself and to others and their response to your behavior. If you apply an optimistic mindset you  will change your life!