DR. JEFFREY KELMAN: John Kennedy was sick from age 13 on. In 1930, when he was 13, he developed abdominal pain. By 1934 he was sent to the Mayo Clinic where they diagnosed colitis or it was called colitis. By 1940 his back started hurting him, by 1944 he had his first back operation, by 1947 he was officially diagnosed as having Addison's Disease.

And he was basically sick from then on through the rest of his life. He had two back operations, in '54 and '55, which failed. And he needed chronic pain medication from '55 through his White House years, until he died in Dallas. He was never healthy. I mean, the image you get of vigor and progressive health wasn't true. He was playing through pain most of the presidency.

Wow, that's incredible that he was able to "play through the pain" like that.

Even great leaders like JFK go through so much more suffering than we realize.