Former President Bill Clinton says his affair with Monica Lewinsky was a way of managing his anxieties.
He made the remarks as part of a documentary series titled "Hillary" which looks at the public life of 2016 presidential candidate Hillary Clinton.
Mr Clinton was impeached in 1998 for lying to investigators about his relationship with Ms Lewinsky. He was acquitted at his Senate trial.
Ms Lewinsky was a 22-year-old White House intern at the time of the affair.
Mr Clinton told documentary makers Hulu: "What I did was bad but it wasn't like I thought, let's think about the most stupid thing I could possibly do and do it."
"You feel like you're staggering around - you've been in a 15-round prize-fight that was extended to 30 rounds, and here's something that'll take your mind off it for a while. Everybody has life's pressures and disappointments and terrors, fears or whatever, things I did to manage my anxieties for years."
His relationship with Ms Lewinsky became a major news story in the late 1990s after the then-president first denied the affair before later admitting to "inappropriate intimate physical contact".
Mr Clinton's initial response to the media reports in 1998 - "I did not have sexual relations with that woman" - has gone down as one of US politics' most memorable quotes.
Ms Lewinsky has maintained that her relationship with the former president was consensual but she called it a "gross abuse of power".
"Any 'abuse' came in the aftermath, when I was made a scapegoat in order to protect his powerful position..." she told Vanity Fair in 2014.
She said she had "limited understanding of the consequences" at the time and regrets the affair daily.
In the documentary Mr Clinton says he feels "terrible" that Ms Lewinsky's life was defined by their relationship.
"Over the years I've tried to watch her get a normal life back again but you've got to decide how to define normal," he said.
When asked about the incident, Mrs Clinton explained how devastated she was.
"I was so personally, just hurt and I can't believe this, I can't believe you lied. It was horrible and I said if this is going to be public, you have to go tell Chelsea."
She explained how she "didn't want anything to do with him" after news of the affair broke.
"I made a decision to stay with my husband. I think some people thought I made the right decision and some people thought I made the wrong decision.
Mr Clinton told the documentary-makers that telling their daughter Chelsea about the affair was "awful".