Princess Diana reportedly received notes under her door from Prince William and Prince Harry during split

Get ready for your heart to break into a bunch of little pieces. And don't say we didn't warn you.

In anticipation of the ITV documentary airing on Monday in honor of the 20-year anniversary of Princess Diana's death, the late princess' former butler, Paul Burrell (whose ties have since been cut from the royal family), told a touching story about Di and her two boys.

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According to Burrell, during the separation in 1992 (before the official divorce in 1996), "... whenever Diana got upset, they would push notes under her door saying, 'It will be OK'."

See adorable photos of Diana with her two sons:

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Princess Diana with her sons
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Princess Diana with her sons
VENICE, ITALY - MAY 5: (FILE PHOTO) (L-R) Diana the Princess of Wales holds her son Harry, whilst looking at Prince William held by his father Prince Charles on May 5, 1985 in Venice, Italy. Prince William will celebrate his 21st birthday on June 21, 2003. (Photo by Georges de Keerle/Getty Images)
Princes William and Harry with their mother, Diana, Princess of Wales (1961 - 1997) in the garden of Highgrove House in Gloucestershire, 18th July 1986. William is wearing a Dallas Cowboys t-shirt.(Photo by Tim Graham/Getty Images)
TETBURY, UNITED KINGDOM - JULY 18: Princess Diana At Highgrove With Prince William And Prince Harry Dressed In Miniature Parachute Regiment Uniforms And Playing On Their Slide In The Garden (Photo by Tim Graham/Getty Images)
TETBURY, UNITED KINGDOM - JULY 18: Princess Diana With Her Sons Prince William And Prince Harry Playing With A Playhouse In The Garden Of Their Home Highgrove (Photo by Tim Graham/Getty Images)
The Prince and Princess of Wales on holiday with their children, Princes William and Harry, at the Spanish royal residence Marivent Palace, August 1987. (Photo by Terry Fincher/Getty Images)
The Princess of Wales arriving at Aberdeen airport with her sons William and Harry for a holiday at Balmoral Castle, August 1986. Princess Diana is wearing a polo motive sweater by Mondi. (Photo by Jayne Fincher/Getty Images)
UNITED KINGDOM - DECEMBER 01: Prince Charles, Prince of Wales and Diana, Princess of Wales at home in Kensington Palace with their sons Prince William and Prince Harry (Photo by Tim Graham/Getty Images)
LONDON, UNITED KINGDOM - SEPTEMBER 16: Princess Diana And Prince William Leaving After Delivering Prince Harry To Mrs. Mynor's Nursery School. (Photo by Tim Graham/Getty Images)
LONDON, UNITED KINGDOM - JUNE 11: Diana, Princess Of Wales, Holding A Young Prince Harry In Her Arms As She Watches Trooping The Colour With Prince William And Princess Margaret From The Balcony Of Buckingham Palace. (Photo by Tim Graham/Getty Images)
BALMORAL, SCOTLAND - AUGUST 18: Diana, Princess of Wales, and Prince Harry play on the banks of the River Dee, near Balmoral Castle.during a Summer vacation, on August 18, 1987, in Balmoral, Scotland. (Photo by Julian Parker/UK Press via Getty Images)
NECKER ISLAND, BRITISH VIRGIN ISLANDS - JANUARY 9: Diana, Princess of Wales, with Prince Harry ( centre ), and her Niece's and Nephew's on holiday on Necker Island , on January 9, 1989 in Necker Island, British Virgin Islands. (Photo by Julian Parker/UK Press via Getty Images)
BATH - MAY 30: (FILE PHOTO) Prince William, Diana, Princess of Wales, Prince Harry and Charles, Prince of Wales, attend the wedding of the Duke of Hussey's daughter in May, 1989 in Bath, England. (Photo by Anwar Hussein/Getty Images)
LONDON - SEPTEMBER 12: (FILE PHOTO) Princess Diana with her sons Prince William and Prince Harry at Wetherby School on September 12, 1989 in London, England. It is Prince Harry's first day at school. (Photo by Anwar Hussein/Getty Images)
Diana, The Princess Of Wales Takes Her Sons, Prince'S William, And Harry Out On The Boat ' Maid Of The Mist ' To View Niagara Falls. (Photo by Julian Parker/UK Press via Getty Images)
CHERTSEY, UNITED KINGDOM - APRIL 18: Diana, Princess of Wales, with Prince Harry, on the Depth Charge ride at Thorpe Park, Theme Park, on April 18, 1992 in Chertsey United Kingdom . (Photo by Julian Parker/UK Press via Getty Images)
LECH, AUSTRIA - APRIL 10: Princess Diana With Princes William & Harry Skiing In Lech, Austria (Photo by Tim Graham/Getty Images)
Diana Princess Of Wales, Prince William & Prince Harry Visit The 'Thorpe Park' Amusement Park. (Photo by Julian Parker/UK Press via Getty Images)
AUSTRIA - MARCH 30: Lech: Princess Diana, sons William and Harry going to restaurant in calash In Lech, Austria On March 30, 1993. (Photo by Laurent SOLA/Gamma-Rapho via Getty Images)
LECH, AUSTRIA - MARCH 27: Princess Diana With Prince William & Prince Harry In Sleigh During Ski Holiday In Lech, Austria. Behind Are Diana's Friends Kate Menzies And Catherine Soames (Photo by Tim Graham/Getty Images)
LONDON, UNITED KINGDOM - AUGUST 19: Princess Diana, Prince Harry [ Waving ] And Prince William Watching The Parade Of Veterans On V J Day, The Mall, London. Designer Of Diana's Suit - Tomasz Starzewski (please Check - People Magazine, 04/12/1999) (Photo by Tim Graham/Getty Images)
EMBARGOED TO 0001 Sunday July 23, 2017. NO USE AFTER MONDAY JULY 31, 2017. NEWS EDITORIAL USE ONLY. NO USE ON THE FRONT COVERS OF ANY UK OR INTERNATIONAL MAGAZINES. NO COMMERCIAL USE (including any use in merchandising, advertising or any other non-editorial use including, for example, calendars, books and supplements). This photograph (whose copyright is vested in the Duke of Cambridge and Prince Harry) is provided to you on condition that you will make no charge for the supply, release or publication of it and that these conditions and restrictions will apply (and that you will pass these on) to any organisation to whom you supply it. All other requests for use should be directed to the Press Office at Kensington Palace in writing. This photograph released by Kensington Palace, from the personal photo album of the late Diana, Princess of Wales, shows the princess holding Prince William whilst pregnant with Prince Harry, and features in the new ITV documentary 'Diana, Our Mother: Her Life and Legacy', which airs on ITV at 21.00hrs on Monday 24th July.
EMBARGOED TO 0001 Sunday July 23, 2017. NO USE AFTER MONDAY JULY 31, 2017. NEWS EDITORIAL USE ONLY. NO USE ON THE FRONT COVERS OF ANY UK OR INTERNATIONAL MAGAZINES. NO COMMERCIAL USE (including any use in merchandising, advertising or any other non-editorial use including, for example, calendars, books and supplements). This photograph (whose copyright is vested in the Duke of Cambridge and Prince Harry) is provided to you on condition that you will make no charge for the supply, release or publication of it and that these conditions and restrictions will apply (and that you will pass these on) to any organisation to whom you supply it. All other requests for use should be directed to the Press Office at Kensington Palace in writing. This photograph released by Kensington Palace, from the personal photo album of the late Diana, Princess of Wales, shows the princess and Prince Harry on holiday and features in the new ITV documentary 'Diana, Our Mother: Her Life and Legacy', which airs on ITV at 21.00hrs on Monday 24th July.
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If that's not enough to warm (or break) your heart, the boys, around 10 and 8 years old at the time of the split, would also often sleep in Diana's room. And because she knew "how difficult it was for the boys," she apparently tried to keep them as busy as possible.

William and Harry recently opened up about their final conversation with their late mother, and Kensington Palace shared three photos from Diana's personal photo album on Sunday.

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