As a tireless advocate for countless charities, Princess Diana is remembered for her thoughtfulness. She was also a dedicated writer of thank-you notes, sending multiple a day regardless of what else was going on in her life.

According to Harpers Bazaar, in a handwritten message from 1996, she warmly thanks her friend Simon Barnes for his Christmas gift. According to RR Auction, "Barnes, a paraplegic who broke his back on a Territorial Army assault course at the age of 21, developed a friendship with Diana through their shared efforts with the International Spinal Research Trust."

This isn't your average thank you note, though. The auction house estimates it will sell for over $2,000 because of its very special contents. "Diana had such an openness, and engaging quality — that's what everyone loved about her, and that can be seen in this letter," said Robert Livingston, Executive Vice President at RR Auction.

If you can't decipher her loopy cursive, the note reads:

I was enormously touched to receive your lovely present — I have not read 'The Celestial Prophecy' & I'm relying on you to alert me to these great books! Thank you so much for thinking of me at Christmas time — After all the changes that have taken place this year it's marvelous of you to be so thoughtful. I hope 1997 will be a happy year for you — personally I can't wait to get out of this one! Lots of love, Simon, & a huge heartfelt thank you for my book.

The letter is written on Kensington Palace stationary, her royal home since 1981. As for the gift, Diana mentions "The Celestial Prophecy," but she's likely referring to the famous adventure novel The Celestine Prophecy by James Redfield. The New Age spiritual guide became an international bestseller that year.

Most importantly, the message takes on a special meaning considering the events of 1996. Only a few months earlier, Diana and Charles finalized their divorce, explaining her impatience for the new year. Sadly, 1997 only brought even more tragic news as it would be the last year of her life.

"The letter from Lady Diana shows her caring loving side, that each of us can instantly recognize — and remember about her — even when her own marriage may have been was falling apart," Livingston said. It's only fitting that for her last Christmas, the people's princess expressed her gratitude for others.