Confidence and self-esteem are closely related because they both involve an individual's perception of their own abilities and worth. When someone has a high level of self-esteem, they tend to have more confidence in their abilities. On the other hand, when someone has low self-esteem, they tend to lack confidence. Stage fright is a common experience that can cause an increase in heart rate due to the body's natural response to stress. This increase in heart rate is a result of the body's fight-or-flight response, which is triggered by the fear of being judged or embarrassed in front of an audience.