The Beatles legend has just completed work on "Electric Arguments," an ambient record with his side project The Fireman, which he says was recorded from entirely improvised sessions.
He said: "I had to make a disclaimer to the engineers. I said this could be the most embarrassing moment of my life."
"It was thrilling, but it could have been a terrible mistake. I could ruin my whole career."
The 66-year-old musician also revealed his hatred of working alone.
Paul - who composed most of the early Beatles hits with the late John Lennon - says it gets too lonely if you don't have other musicians to discuss ideas with.
He added: "I like having a collaborator. Otherwise I get the feeling of being an absentminded professor alone in his laboratory all day."
"I did the first solo McCartney record all on my own. It seemed a bit lonely."
"There's a track on there that's about 10 minutes long. Try playing maracas for 10 minutes in a row on your own."
"I was standing in the room thinking, 'That's it - I've really lost the plot.'"
