Sir Paul McCartney didn't know if he should keep making music after the Beatles split up.
The 80-year-old musician thinks the biggest professional risk he ever took was launching his band Wings with late wife Linda McCartney in the wake of the Hard Day's Night hitmakers going their separate ways in 1970.
Answering a fan question from Twitter about his biggest professional risk, he wrote on his website: "The main question I had was whether to keep going after The Beatles because it was a hard act — some might say, an impossible act — to follow.
"The ingredients in the Beatles were so unique.
"You had John right there, who could have made any group brilliant. Then you had George's talent, and Ringo's, and then me.
"Once that band had finished, I didn't know what to do with myself, and trying something new was really risky.
"Then, of course, having Linda in Wings, when she was not a 'musician', was a risk too. When the reviews started to come in a lot of them focused on her, asking, 'What's she doing in the band?' And that was hurtful.
"But I rationalised it by thinking about when we started The Beatles and none of us knew our chords - over time we got better and picked things up."
Paul admitted the early days of Wings made him feel like he was "earning [his] fame again".
He continued: "In the early days of Wings, we decided to go right back to square one, taking a van up the motorway and playing little spontaneous gigs at universities for students, rather than jumping straight in with big live shows.
"I'd doubled back to almost being nothing - just some guy in the band - and now I was earning my fame again.
"By the time the mid-70s came around when we were doing a big American tour, that was the vindication of it. We were so tight and had come up together, as it were. The risk paid off."
The Live and Let Die singer noted he isn't usually a risk taker and was unsure what was the right move to make if he wanted to keep making music.
He said: "I'm quite careful normally. There's a couple of times in life when you are forced into taking a risk.
"After The Beatles, this was my situation: 'Do I keep going with music, or not?' Well, I want to keep going. So, 'How am I going to do it? Am I going to have a band, or am I just going to busk outside train stations? How's it going to work?' "
Paul noted his late bandmate John Lennon was the "polar opposite" so his willingness to take risks made him someone who "was very exciting to be around".
He added: "Obviously, I'm not completely square. I do a lot of zany stuff! That's in my character too, but I don't live my life as a risk-taker. I try and work it out to some extent."