We explain our behavior in terms of the payoffs we receive for engaging in that behavior. In fact, it was sort of fun trying to get a rhythm to the task. Beyond that, we will come to enjoy intrinsically rewarding activities less when there is an external reward associated with it. Reading programs for children that provide money or pizza for the number of books read actually end up decreasing the number of books read by those children once the external rewards are removed. The children explain their behavior by showing that they engaged in the activity not for the pleasure of reading, but for the money or pizza.
Most people rate themselves above average, but less than ideal.
This is often called the Self-centered bias. Most people will disobey a person in authority who orders them to hurt a stranger. Unfortunately, this is false. The most classical experiments on this were performed by Stanley Milgram. In his studies, he had an experimenter in a white lab coat instruct a research subject to deliver ever-increasingly strong shocks to another person, believed to be another subject.