Quick Definition: When an artist does something or takes on the mindset of doing things simply for his own amusement, and not to get a reaction from a girl or another person of higher social value.
Personal amusement is the idea that an artist can tell a joke or do something in a club simply for his own amusement. This very powerful mindset is often contagious and very attractive.
Many guys go out to clubs and feel fear, or feel afraid to approach girls. Sometimes, they lack intent when they obviously are hitting on them, which presents a chicken frame to women. Instead, the opposite of this is when a guy does something simply for his amusement. An example would be dancing somewhat clumsily but doing it with such fun and conviction that others start to imitate you. Most guys are too afraid or confined in their own heads to own up to a dance floor.
Sometimes too much action for simple personal amusement can result in consequences, such as acting ludicrous at a job. As such, personal amusement usually works in a bar situation or in situations where people do not have direct power over you.
Conan, during his off TV moment, on how he wins the Google crowd through personal amusement + an amazing skill set in comedy: