Diane Sawyer Talks With Nancy Reagan

June 28 -- For nearly seven years, Nancy Reagan has been her husband's voice, his public face, and the guardian of the legacy of the man whose presidency dominated U.S. and world affairs in the 1980s.

A new book released by the Ronald Reagan Library, Ronald Reagan, an American Hero, recounts her husband's golden days, as well as his twilight. It describes through pictures and narrative his life from birth to his days as an actor, to governor of California to presidency of the United States, to the present, including many pictures from the former first lady's private collection. (Click here to read an excerpt of the book.)

ABCNEWS' Diane Sawyer sat down with Mrs. Reagan and got an intimate portrait of what her life with the former president is like today. The following excerpts are taken from their conversation, beginning with her description of how they came to tell the world about his condition, while looking at the original copy of the letter in which Ronald Reagan disclosed the disease to a stunned nation.

'Eternal Optimist'

Nancy Reagan: So we just went into the library and he sat down at the table. And he wrote it, gave it to me to read and that was it.

Diane Sawyer: And did he ever express fear to you?

Reagan: Never, never. I mean, in that letter, it [says it] "Now begins the journey that will lead into the sunset of his life."

Sawyer: (reading from the letter) "I know that for America, there will always be a bright dawn ahead."

Reagan: [The] eternal optimist.

Physical Decline

Reagan: But, you know, Diane, there's so many, many people who are doing exactly the same thing as I'm doing. And actually I have some advantages that they don't have. I mean, I have the Secret Service. Emotionally we're in the same spot, all of us, but there are a lot of people out there who are going through this.

Sawyer: How many days do you say, "I can't do it. I cannot get through another day."

Reagan: You just don't say that. (Laughing) You don't.