How could he refer to that impending doom as the sunset of his life? Was he ignorant of the disease? Not at all. As president, Reagan made eight separate statements on Alzheimer’s—an average of one for each year in the White House. It is chilling to read those words today. Alzheimer’s, said Reagan, is an “indiscriminate killer of mind and life”—a “devastating” sickness that “deprives its victims of the opportunity to enjoy life.” It “ranks among the most severe of afflictions, because it strips people of their memory and judgment and robs them of the essence of their personalities. As the brain progressively deteriorates, tasks familiar for a lifetime, such as tying a shoelace or making a bed, become bewildering. Spouses and children become strangers.” “Slowly,” reported Reagan, “victims of the disease enter profound dementia.”

Reagan had unwittingly forecast his own demise.

So, how could Reagan, obviously knowledgeable of Alzheimer’s, describe the onset of his disease as a coming sunset? I’ve watched sunsets on the California coast, indeed from the very “Ranch in the Sky” that Reagan did. The answer was Reagan’s secret weapon: his optimism. He called it an eternal optimism, a “God-given optimism.”

He first discovered that gift through his mother, Nelle Reagan, who (along with Nancy) was the most important person in his life. Nelle instilled in her son the Christian faith so fundamental to his very being. She taught him that the twists and turns in the road are there for a reason. The bad things are part of “God’s plan” for the good. There is a rainbow waiting around the bend. God, Reagan reasoned, was in control and worked everything for the best.

Reagan preached this theology in his memoirs and in countless private letters that today sit in the Reagan Library. It became a kind of grief ministry. He would write to a widow: It’s a tragedy that your husband died and I write to send my deepest condolences; if it’s any comfort, God has a plan…

In 1962, the woman who shared such thinking with Reagan died of what the family called “senility;” what we today would likely diagnose as Alzheimer’s. Yet, Reagan remained optimistic. His mother’s death, he told friends, was a step through an eternal window—to that rainbow waiting around the bend.

“How we die is God’s business,” Reagan told his daughter Patti. Our duty is to accept it. As a 17-year-old, he wrote a poem called “Life.” Here is a revealing excerpt:

[W]hy does sorrow drench us
When our fellow passes on?
He’s just exchanged life’s dreary dirge
For an eternal life of song.

All of this explains how the eternal optimist, in that November 1994 letter, could be positive even as Alzheimer’s was crowding in, about to cast his mind into oblivion.

It is telling that in that brief letter to the American people, Ronald Reagan mentioned God and faith four times. “When the Lord calls me home,” he wrote, “I will leave with the greatest love for this country of ours and eternal optimism for its future.”