The 76-year-old musician in the Sunday Times interview said that he had become very humble through experience.
"It was huge, a huge wall that I did not see above and I was at the bottom, everyone would say it was just a medicine, hallucinations, but we felt we'd seen something bigger," he said.
The Beatles' music was the last year in which the psychedelic medicine was activated.
McCartney also said to himself that he believed that lost loved ones, including the late wife Linda, viewed him from heaven.
The singer is currently publishing her new album and tours. He is still one of the most popular artists.