Houston drowned Feb. 11 in a hotel bathtub after using cocaine. She was 48.
"I could have so easily ended up like Whitney Houston," John told E! News Thursday.
"It's a miracle I didn't," the 65-year-old singer said. "Because I'm sure I did as much cocaine as she ever did."
John chalked his recovery up to the willpower to take back his life.
"I would not be the person I am today [if I hadn't]," he said. "I wouldn't have [my son] Zachary, [my husband] David [Furnish]. I wouldn't have anything. I'd probably be dead."