"ask not what your country do for you, ask what you can do for your country."
John F. Kennedy was in poor health as a child. He was diagnosed with Addison's Disease meaning his body did not produce enough cortisol leading to muscle weakness, depression, tanned skin, and more.
Kennedy joined the Navy in World War II. He was given command of a boat called PT-109 in the Pacific. During this time, his boat was rammed by a Japanese destroyer and he and his crew were thrown into the water. Due to his efforts, he swam back four hours to shore saving a crewman at the same time.
Kennedy won a seat in the House of Representatives in 1947 where he served for three terms. He was elected to the US Senate in 1953.