We form certain expectations of people or events. We communicate these expectations with various cues. People tend to respond to these cues by adjusting their behavior to match them. The result is that the original expectations often become true. This creates a cycle of self-fulfilling prophecies.
Low expectations lead to low performance.
Lower performance resulting from low expectations lead us to like someone less. We tend to be comfortable with people who meet our expectations. We tend to be uncomfortable with those who do not meet our expectations, either high or low. Forming expectations is natural and unavoidable. Once formed, expectations about ourselves tend to be self-sustaining.