Sir Paul McCartney revealed that he started drinking heavily and almost quit music after The Beatles split in 1970.
The music superstar said he formed follow-up band Wings - which featured his former wife Linda - when he stopped enjoying the party lifestyle.
Reflecting of The Beatles' breakup on Radio 4, Sir Paul said: "I was breaking from my lifelong friends, not knowing whether I was going to continue in music.
"I took to the bevvies. I took to a wee dram. It was great at first, then suddenly I wasn't having a good time. It wasn't working. I wanted to get back to square one, so I ended up forming Wings".
Sir Paul also acknowledged that some of the criticism levelled at Wings was fair but he doesn't regret collaborating with Linda, who died in 1998.
He said: "To be fair we weren't that good. We were terrible. We knew Linda couldn't play but she learnt and, looking back on it, I'm really glad we did it.
"I could have just formed a supergroup and rung up Eric Clapton and Jimmy Page and John Bonham, but we graduated from playing universities to town halls, which was quite funny as I'd been at Shea Stadium quite recently.
But you still remember the names of the people who gave you really bad, vicious reviews: Charles Shaar Murray shall ever be hated!"
Sir Paul also revealed how glad he was to repair his relationship with John Lennon before he was shot dead in 1980.
Their relationship became strained because of business matters but Sir Paul said: "I was really grateful that we got it back together before he died. Because it would have been very difficult to deal with if... well, it was very difficult anyway".
After playing a few bars of Here Today, the song he wrote about Lennon in 1982, he said: "When I was thinking of all the things I never said to him. I'm quite private and don't like to give too much away.
"Why should people know my innermost thoughts? But a song is the place to put them. In Here Today I say to John, 'I love you'.
"I couldn't have said that to him unless we were extremely drunk - I love you, man! But you can put these emotions, these deeper and sometimes awkward truths, in a song".
He admitted the competition he felt with Lennon helped him to create some of his best work.
After being asked if it is harder to write songs as he gets older, Sir Paul replied: "In concerts I'm singing these songs by this 20-something- year-old kid and I'm thinking: 'Why are these songs so good?'