The former military man said he had planned to shoot himself during a trip to France - until his mother made him take her along.
'I got in my car and loaded a few things up to get on the ferry to go to France - to shoot myself,' he said.
The former military man told Inside Edition he had planned to shoot himself during a trip to France - until his mother made him take her along
'Then my mother insisted on coming with me. If she hadn't, I would probably have shot myself. So I owe her my life really.
'I felt I had let people down - probably myself, my family, my friends, the nation, the army, my regiment. Other than that, no one at all.'
Hewitt, 52, opened up about life after Diana during an interview on U.S. television show Inside Edition.
The Princess, who died aged 36 in August 1997, acknowledged her affair with the former household cavalry officer after her divorce from Prince Charles.
Affair: Diana blushes as she presents James Hewitt with the Captain and Subalterns Cup after he led his army polo team to victory at Tidworth in 1989 - at the height of their affair
By royal admission: Princess Diana, who died aged 36 in August 1997, acknowledged her affair with the former household cavalry officer after her divorce from Prince Charles
Rumours later circulated that Hewitt, not Charles, could be the father of Diana's son Prince Harry.
But the ex-army man has claimed the young Prince was born before he and Diana began their affair.
Hewitt has always denied that he is the father of Prince Harry
'No I am not,' he said, when asked once again whether he was Harry's father. 'I am not happy talking about it. It's out of respect for everyone.'
Hewitt came under fire for trying to sell love letters he received from Diana for £10 million.
He also helped write a book about the Princess following her death, but insists he still misses her.
'I think we all miss her,' he said. 'But I've tried to move on with my life.'
The full interview with Hewitt airs in the United States today.
It was revealed last week that Hewitt is to trade upon his increasingly tenuous links to the Royal Family by throwing a Royal Wedding party at his bar in Spain – with himself as ‘guest of honour’.
He has been living in Marbella in exile after his scandalous attempt to sell her letters for £10 million.
The ‘comeback cad’, as he’s been dubbed, has cheekily given his approval for Prince William and Kate Middleton’s wedding and is planning a lavish Royal-themed day at his bar, Polo House, on April 29, complete with a big screen showing the ceremony.
Diana admitted to having the five-year affair during her sensational Panorama interview in 1995.
He first met Princess Diana at a party in London's Mayfair in 1986. She was 25, he 28.
Although six years ago, he was hypnotised for a television programme in which he 'revealed' that his affair with Diana had begun earlier than he had previously stated, commencing in 1982, not 1986 - before the birth of Prince Harry.
In another interview on Larry King Live in 2003, Hewitt discussed his relationship with the princess, the controversy over his going public with her personal correspondence and recent press reports of his attempts to auction the letters
When they met, Diana was in the middle of a famous 39-day trial separation from her then husband Prince Charles.
Diana took Hewitt on as a horse-riding instructor for her and her two sons. Their relationship lasted until 1992 when Diana is reported to have stopped taking Hewitt's calls.
In 1994 Hewitt broke cover and collaborated with writer Anna Pasternak on Princess In Love, a sordid account of his affair with Diana.
Diana was said to be distraught by this betrayal, telling Martin Bashir in the Panorama interview: 'Yes, I adored him. Yes, I was in love with him. But I was very let down.'
'I was in love with him': Diana admitted to having the five-year affair during her sensational Panorama interview in 1995
Hewitt later tried to tried to sell 60 love letters he received from the Princess for a reported £10million.
In 1999, two years after Diana died in Paris, he published his autobiography, Love and War in which he revealed intimate details about his affair.
He told how Diana seduced him and how they made love in her four-poster bed and on a bathroom floor.