Acharya Prashant discusses the fundamental difference between choosing a career based on passion versus choosing it based on 'mustness' or dharma. He explains that what people commonly call passion is often just a result of external conditioning and social surroundings, rather than an internal urge. For instance, a person's interest in a specific sport is usually determined by their environment and upbringing rather than an innate calling. Therefore, choosing a path based on passion is only marginally better than choosing one based on external pressure or coincidence.