Sylvester Stallone has admitted the success of Rocky made him "insufferable" and think he was "an authority on everything".
"I abused power badly," the US star told host Jonathan Ross during an on-stage interview at the London Palladium on Saturday.
"I read some of the interviews I gave now and wish I could go back and punch myself in the face," he continued.
But he added a dismal showing of a later film brought him back to Earth.
Stallone had left the set of Rocky II to attend a first-day showing of 1978 drama Paradise Alley, only to find there were just two people in the audience.
"And one of them was asleep," he sighed, admitting it had been "a humbling experience" but "a good thing" for him in the long run.
Described as An Evening with Sylvester Stallone, the West End event saw the 67-year-old entertain an audience of appreciative fans with anecdotes spanning the breadth of his four-decade career.
Billed as Stallone's "first West End debut", the 90-minute interview also saw the star of the Rambo and Expendables films show another side to his macho persona.
Bursting into song at one point, he impressed at another by reciting a short passage from Shakespeare's The Comedy of Errors.
The evening climaxed with him being inducted into the London Palladium Hall of Fame - an accolade previously bestowed upon Frank Sinatra, Liza Minnelli and Andrew Lloyd Webber.
Discussing the genesis of boxing classic Rocky, Stallone revealed he had been offered up to $300,000 - "a million dollars today" - to let the film be made with another lead.
The Italian-American said it had been a "crossroads moment" in his life, but that he knew he would have "hated" himself had he not stuck to his guns.
The uplifting tale of a lowly debt collector who gets a shot at the world heavyweight title became a box office smash, going on to win three Academy Awards.
Five sequels followed, starting with Rocky II in 1979 and culminating with 2006's Rocky Balboa - which Stallone said was "unquestionably" his favourite.
The actor may reprise his signature role in Creed, a spin-off film that would see the older Balboa train the grandson of a former adversary.
"People think it's Rocky VII but it's not," he said, adding it would be "a very interesting challenge" to revive the character in a different guise.
The actor's John Rambo character, introduced in 1982's First Blood, has enjoyed similar longevity, going on to appear in three more movies.
On Saturday, however, Stallone said the series had "maybe run its course", joking that he would only consider reviving his celebrated commando character if he could be a security guard in Las Vegas.
Moving on to his fellow action leads, Stallone expressed admiration for Expendables co-star Jason Statham, while admitting that he and Arnold Schwarzenegger had "hated each other" during the height of their action careers.
Yet he had little to say about Bruce Willis, whom he called "greedy and lazy" last year in a widely publicised Twitter rant.
There was also no mention of Stallone's actor son Sage, who was found dead last year at his Hollywood home at the age of 36.
Stallone has been in London promoting his new boxing comedy Grudge Match alongside co-star Robert De Niro.
The Palladium event followed a similar one last June, at which Al Pacino took questions about his life and career.