John, 65, who has battled drink and drugs addiction, said he was a huge cocaine addict during his friend Ryan White's plight and up to his death in 1990, reported Contactmusic.
"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," John said in his forthcoming book, 'Love is the Cure: On Life, Loss and the End of AIDS'.