Conversation so far:
What kind of illness did O'Neill have?
O'Neill ultimately faced a severe Parkinsons-like tremor in his hands which made it impossible for him to write during the last.
How long did he suffer from this disease?
write during the last 10 years of his life.
Is that what killed him?
problems (including depression and alcoholism.
Was his death caused by health problems or suicide?
O'Neill ultimately faced a severe Parkinsons-like tremor in his hands.
What year did he die?
on November 27, 1953, at the age of 65.
Are there any other interesting aspects about this article?
65.
As he was dying, he whispered his last words: "I knew it.
I knew it.

Question: What was he referring to?
Self-contained rewrite: What was Eugene O'Neill referring to when he whispered "I knew it. I knew it" as he was dying?