Sir Elton John believes he would be dead if it was not for his late friend who died of AIDS aged 18.
The 65-year-old singer - who has battled drink and drugs addiction - admits he was a "huge cocaine addict" during his friend Ryan White's plight and up to his death in 1990, but the teenager played a big part in inspiring the Rocket Man hitmaker to take stock of his life and conquer his addictions.
In his forthcoming book, Love is the Cure: On Life, Loss and the End of AIDS, serialised in the Mail On Sunday, he wrote: "Ryan was a true hero, a true Christian, because he unconditionally forgave those who made him suffer. Ryan changed the course of a deadly epidemic and helped save millions of lives.
"But when Ryan died in April 1990 at the age of 18, I didn't know how to speak to someone unless I had a nose full of cocaine and a stomach full of alcohol. After his funeral, I returned to London and locked myself away at home, as had become my habit.
"My sense of values was buried under my self-destruction. But I'm here today because of Ryan."
The musician - who has raised more than $342million ($NZ) for the Elton John AIDS Foundation - still feels "deeply ashamed" that he did not do more about the AIDS epidemic, and he believes it is a "small miracle" that he never contracted HIV.
He added: "I'm deeply ashamed that I did not do more about AIDS back then when my friends, including Ryan, were dying all around me. I just did not have the strength or sobriety to do anything about it.
I would go to funerals, I would cry, I would mourn, sometimes for weeks. And my behaviour got worse, I was sleeping around without protection and it is a small miracle that I never contracted HIV myself.
I remember watching television after Ryan's death and seeing footage of the funeral. It was one of the lowest points of my life.
"My hair was white, my skin pale. I was bloated and gorged. I looked tired, sick and beaten. I looked horrible. It was almost too much to take. I had been overcome by addiction; I was completely out of control. I looked, quite frankly, like a piano-playing Elvis Presley.
"As messed up as I've ever been. There was no question: I was going to change, or I was going to die."