As a graduate student, Hawking gradually started showing symptoms of tripping and general clumsiness. His family became concerned when he was home during his Christmas break from school and they insisted he see a doctor.
Before seeing a specialist, however, he attended a New Year's party where he met his future wife, Jane Wilde. She remembers being attracted to his "his sense of humor and his independent personality."
He turned 21 a week later, and shortly after he entered the hospital for two weeks of tests to discover what was wrong with him. He was then diagnosed with amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, which is a neurological disease that causes patients to lose control of their voluntary muscles. He was told he'd probably only have a few years to live.
Hawking remembers being shocked and wondering why this happened to him. However, seeing a boy dying of leukemia in the hospital made him realize that there were others worse off than him.
Hawking became more optimistic and started dating Jane. They were soon engaged, and he cites their engagement as giving him "something to live for" [source: Larsen].