Former Sun editor Rebekah Brooks told a court the newspaper's coverage of boxer Frank Bruno's mental breakdown was a "terrible mistake".
The 45-year-old said she approved the tabloid's front page story featuring the headline "Bonkers Bruno Locked Up" about the sports star's health problems in 2003.
She told the hacking trial at the Old Bailey she only realised her "blind spot" when she returned home and was alerted by her then-husband Ross Kemp.
Brooks said: "I personally made lots of mistakes during my 10-12 years as a newspaper editor….Some of which I felt were big mistakes I have tried to address.
"The Sun had a good relationship with Frank Bruno. We did lots of interviews.
"He was a great character, very friendly to the media.
"This day I was involved in many, many meetings.
"I hadn't really got on top of what happened to Frank Bruno."
Brooks, of Churchill, Oxfordshire, said she was shown a proof version of the Sun's front page covering the story and gave her approval.
She went on: "I got home, put the proof down and Ross said, 'what is that? What are you doing?'.
"Looking again it was a complete blind spot.
"Ross had seen the front page and questioned how brutal it was. It was a terrible mistake I made."
Brooks said the headline was changed but featured in 15,000 of the Sun's four million copies that day.
"He had not been well and we talked to him about it obviously," she said.
"We did everything we could to make up for this copy that had gone out and indeed we did make up for it I think.
"I wanted to show in this flash of speed you can miss something perfectly obviously wrong and this was one of my worst ones at the Sun."
Brooks, who denies conspiring to hack phones, conspiring to commit misconduct in public office and conspiring to cover up evidence to pervert the course of justice, took to the witness box today for her fifth day of evidence.
Under questioning from her lawyer Jonathan Laidlaw QC, Brooks was also asked about the Sun's coverage of the death of serial killer Harold Shipman in 2007 when it ran the headline "Ship Ship hooray!".
Wearing a navy blue and white patterned top and a blue pashmina draped around her shoulders, Brooks said it was in response to the home secretary at the time releasing a statement that he was opening a bottle of champagne to celebrate the news, but admitted the headline was in "bad taste".
The former News International chief executive also described the paper's response to former Labour MP Clare Short's campaign against Page Three as "cruel and harsh".
"It was just again too personal and just wrong," she said.
Brooks told jurors the paper went too far in the way it treated Sharon Shoesmith, the social services boss who lost her job over failures in relation to the death of Baby P.
She said: "In the furore and the passion or obsession if you like, we were trying to get this campaign and trying to get justice for Baby Peter, our attack on her was again probably too cruel and harsh and over the top."