Washington (CNN) -- She wrote of being in love, falling out of love, fearing a marriage to a skirt-chaser and then loving that marriage, and believing in God to hold on to the hope of reuniting with her assassinated husband.
Letters that a young Jacqueline Bouvier, and later a married Jackie Kennedy, wrote to a Catholic priest in Ireland offer a rare and revealing glimpse of the private thoughts of one of America's most admired first ladies.
An icon of style and elegance, she came to symbolize an administration nicknamed Camelot that ended with the violent death of President John F. Kennedy in November 1963.
Over a period from when she first met the Rev. Joseph Leonard on a trip to Ireland in 1950 until he died in 1964, she wrote him more than two dozen letters.
She only met him in person once more, in 1955, but the letters being sold at auction in Ireland provide insight into the personal dreams, wishes and fears of a young woman who became one of the world's most popular figures.
Part of her popularity involved the mystique of Jackie Kennedy, the focus of near-rabid media attention who later married Greek shipping magnate Aristotle Onassis. While others sought to chronicle the woman and her life, she provided little help through the years.
"It's so good in a way to write all this down and get it off your chest - because I never do really talk about it with anyone," she said in one letter.
The correspondence shows the maturation of a high society girl who broke off an engagement with New York stockbroker John Husted before she met the dashing young politician she would marry.
"So terribly much in love -- for the first time -- and I want to get married. And I KNOW I will marry this boy," she wrote of Husted. "I don't have to think and wonder -- as I always have before -- if they are the right one, how we'd get along etc. ... I just KNOW he is and it's the deepest happiest feeling in the world."
Things changed, as she later described to Leonard.
"I'm ashamed that we both went into it so quickly and gaily, but I think the suffering it brought us both for a while afterwards was the best thing -- we both need something of a shock to make us grow up," she wrote. " I don't know if John has -- I haven't seen him and I don't really want to, not out of meanness -- it's just better if that all dies away & we forget we knew each other -- but I know it's grown me up and it's about time!"
The next time she gets engaged, she added, it will be "ALL RIGHT and have a happy ending!"
"His career is the driving thing"
That next time was to Kennedy, the scion of an influential Democratic family from Massachusetts who became the first U.S. president of the televised campaign era.
"If he ever does ask me to marry him, it will be for rather practical reasons - because his career is this driving thing with him," Jackie wrote in one letter of Kennedy's political ambitions. A 1952 letter, written the year before they wed, showed her understanding of Kennedy's philandering ways, which continued in the White House.
"He's like my father in a way — loves the chase and is bored with the conquest — and once married needs proof he's still attractive, so flirts with other women and resents you," she wrote. "I saw how that nearly killed Mummy."
She also wondered about the glitzy life she lived, writing that "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," she added.
"God will have a bit of explaining to do"
Despite such concerns, she later wrote Leonard that she loved being married to the man she called Jack. After Kennedy's assassination, Jackie wrote of trying to understand it all.
"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," she wrote." God will have a bit of explaining to do to me if I ever see him."
Another passage showed the depth of her grief.
"I have to think there is a God -- or I have no hope of finding Jack again," she wrote.
Jackie died in 1994.
The letters to Leonard go up for sale next month at Sheppard's Irish Auction House.
In effect, an "unpublished autobiography"
"We are thrilled at Sheppard's to offer what is in effect the unpublished autobiography of Jacqueline Bouvier Kennedy," said a statement by Philip Sheppard, the auctioneer.
He told CNN on Tuesday the letters came from a private source and as a trained historian, he satisfied himself that "the source who gave the letters is authentic and that the letters are authentic as well."
Jackie was 21 when her correspondence began with the 73-year-old Leonard, and her letters to the priest showed the value she placed on their relationship.
In one, she discussed the difference between Leonard and the American priests she knew, complaining they gave her "a whole lot of trite little phrases that make you angry & resentful and farther away from the church than ever."
By contrast, she wrote, Leonard was "someone who loves everything I love -- who you can have FUN with -- who can take you to Jammet's & the theatre as naturally as to Mass -- whom you can talk to about anything in the world and know you won't shock them -- and whose whole life is built on love -- love and not fear -- which is what always put me off."
One letter to Leonard ended: "I REALLY must stop now Father L -- but bushels, barrels carts & lorry loads of love to YOU -- Jacqueline XO."
CNN's Becky Perlow contributed to this report.