Shortly after his 21st birthday, Hawking is diagnosed with Amyotrophic Lateral Sclerosis (Lou Gehrig’s Disease). Doctors predict that he will not live long enough to complete his doctorate at Cambridge due to his deteriorating health. Hawking relates his feelings at the time:
The realization that I had an incurable disease that was likely to kill me in a few years was a bit of a shock. How could something like this happen to me? However, while I was in the hospital, I had seen a boy I vaguely knew die of leukemia in the bed opposite me, and it had not been a pretty sight. Clearly there were people who were worse off than me—at least my condition didn’t make me feel sick. Whenever I feel inclined to be sorry for myself, I remember that boy.