Letters written to a priest in Dublin have revealed Jackie Kennedy's struggle with God in the aftermath of her husband JFK's assassination.
Her inner difficulties were expressed in private letters written to Vincentian Father Joseph Leonard.
Excerpts have been published in The Irish Times ahead of the letters being auctioned in June.
"I am so bitter against God," the former first lady wrote in one letter written in January 1964, a few months after JFK's assassination on 22 November 1963.
The letters reveal the extent to which JFK's assassination shook her Catholic faith.
"I have to think there is a God - or I have no hope of finding Jack again," she wrote.
"I think God must have taken Jack to show the world how lost we would be without him. But that is a strange way of thinking to me - and god will have a bit of explaining to do to me if I ever see him."
The collection of 33 handwritten letters date from 1950 and 1964. In one, she likens JFK to her father, John 'Black Jack' Vernou Bouvier, because of his womanising ways.
"He's like my father in a way - loves the chase and is bored with the conuest - and once married needs proof he's still attractive, so flirts with other women and resents you. I saw how that nearly killed Mummy," she writes in one letter written in 1952, the year before she married JFK.
She writes later in 1953: "Maybe I'm just dazzled and picture myself in a glittering world of crowned heads and Men of Destiny - and not just a sad little housewife ... That world can be very glamorous from the outside - but if you're in it - and you're lonely - it could be a Hell."
However, she appears by 1954 to have settled into her marriage: "I love being married much more than I did even in the beginning."
Leonard, who died in 1964, wrote letters back to Jackie and also sent her books. They met in 1950, when Jackie was touring Europe with her stepbrother, and in one letter, she reveals how much she valued the exchange.
"Does it give you a sense of power to think you're molding someone else mind and taste? I hope it does and certainly no one ever had a more willing piece of putty to work with," she said.
One letter is affectionately signed off: "I REALLY must stop now Father L - but bushels, barrels carts & lorry loads of love to YOU - Jacqueline. XO."
The collection, which includes a Christmas card signed by Jackie and JFK, is expected to fetch over a million euros when it goes up for auction at Sheppard's Irish Auction House in Durrow, Co Laois.