What is the Beatles song “Let it Be” about?

I was going through a really difficult time around the autumn of 1968. It was late in the Beatles’ career and we had begun making a new album, a follow-up to the “White Album.” As a group we were starting to have problems. I think I was sensing the Beatles were breaking up, so I was staying up late at night, drinking, doing drugs, clubbing, the way a lot of people were at the time. I was really living and playing hard.

The other guys were all living out in the country with their partners, but I was still a bachelor in London with my own house in St. John’s Wood. And that was kind of at the back of my mind also, that maybe it was about time I found someone, because it was before I got together with Linda.

So, I was exhausted! Some nights I’d go to bed and my head would just flop on the pillow; and when I’d wake up I’d have difficulty pulling it off, thinking, “Good job I woke up just then or I might have suffocated.”

Then one night, somewhere between deep sleep and insomnia, I had the most comforting dream about my mother, who died when I was only 14. She had been a nurse, my mum, and very hardworking, because she wanted the best for us. We weren’t a well-off family- we didn’t have a car, we just about had a television – so both of my parents went out to work, and Mum contributed a good half to the family income. At night when she came home, she would cook, so we didn’t have a lot of time with each other. But she was just a very comforting presence in my life. And when she died, one of the difficulties I had, as the years went by, was that I couldn’t recall her face so easily. That’s how it is for everyone, I think. As each day goes by, you just can’t bring their face into your mind, you have to use photographs and reminders like that.

So in this dream twelve years later, my mother appeared, and there was her face, completely clear, particularly her eyes, and she said to me very gently, very reassuringly: “Let it be.”

sources : https://mattandjojang.wordpress.com/2009/05/03/the-story-behind-paul-mccartneys-song-let-it-be/