Multiple theoretical approaches exist within psychology. Seven of these approaches are evolutionary, biological, behavioral, cognitive, humanistic, psycho-dynamic, and socio-cultural. The theoretical approach which best explains John F. Kennedy's behaviors and successes is the socio-cultural approach. The socio-cultural approach uses the culture and society of an individual to define his or her cognition (mental processes).
John F. Kennedy was both successful and secretive. Kennedy was responsible for the establishment of the Peace Corps, received multiple military awards (including a Purple Heart), won a Pulitzer Prize, signed the Nuclear Test Ban Treaty, and promoted space exploration (specifically walking on the moon). As for his secretive side, JFK suffered from many ailments. He took a multitude of medications, and even an anti-psychotic. Only a few people knew how much pain JFK lived with every day.
As for how this fits into the socio-cultural approach, JFK knew that people (the society) would look at him differently if his true medical history (past and present) came out. He also knew that his accomplishments in the military spoke highly to Americans. Essentially, his behaviors and achievements were influenced by how he wanted to be perceived by America (society).