The two letters which talk of her loss are among 30 from an undisclosed source that will be sold at auction in Ireland next month and are expected to fetch at least pounds 1?million.
Over a total of 130 handwritten pages, previewed by the Irish Times, Mrs Kennedy, who died in 1994, confides about her hastily broken-off engagement to a New York stockbroker, her courtship and marriage to Kennedy and her grief and anger over his killing.
Even before her marriage to the future president in September 1953, she wrote with startling prescience about a husband whose vanity and insatiable appetite for womanising would diminish his reputation when it emerged in the years after his death.
"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. I saw how that nearly killed Mummy," she wrote.
In another deeply self-aware letter, written in early 1953, when she was only 23, Mrs Kennedy admits she is consumed with ambition "like MacBeth" while making clear she is under no illusion about the world she is marrying into, a world that for all its flaws she would later deliberately mythologise as "Camelot".
"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."
A year later Mrs Kennedy - who had broken off her engagement to John Husted in March 1952 a few months after it was announced in the New York Times - sounded confident she had made a good decision: "I love being married much more than I did even in the beginning." The letters are part of a correspondence that a 21-year-old Jacqueline Bouvier struck up with Fr Leonard after a visit to Ireland in 1950 when the priest took her to the theatre and dinner at Jammet's, one of the city's best French restaurants.
They will be sold on June 10 at Sheppard's Irish Auction House in Durrow, a small town 66 miles south-west of Dublin, and were described as "the dream find of a lifetime for an auctioneer" by Philip Sheppard, a company spokesman, who refuses to reveal their origin.
President John F. Kennedy and Jackie Kennedy watch the America's Cup race in 1962. Photo / Wikimedia Commons
"They are, in effect, her autobiography for the years 1950-1964,'' he added, describing the archive as primary source material of a kind that has "never before" been offered on the open market. Experts agreed. "What these letters make fascinatingly clear is that - from the very beginning - she knew what she was getting into," said Larry J Sabato, a political scientist and author of last year's The Kennedy Half-Century, which examined how and why the "Camelot" myth so endured among the American public.
"This was not going to be the typical suburban home with two children. She was an extremely bright woman and she's expressing that eternal conflict that other powerful woman must feel," he added.
"Think Hillary Clinton: 'I'm going to be able to do something with my life that I wouldn't be able to otherwise, but I'm also going to have to put up with a lot'.
"They're constantly balancing the rewards and the punishments."
