Dave Benett/Getty Images Princess Beatrice, Sarah Ferguson and Princess Eugenie
Sarah Ferguson is loving life as a "granny."
Fergie, as the Duchess of York is affectionately known, penned an open letter to her daughters Princess Beatrice and Princess Eugenie for Good Housekeeping as the sisters enter a new chapter: starting their own families.
Eugenie, 31, welcomed her first child with husband Jack Brooksbank, a baby boy named August, in February. Meanwhile, Beatrice, 33, is expecting her first child with husband Edoardo Mapelli Mozzi this fall and became a stepmother to Edo's young son from a previous relationship.
"Every day I thank the universe for allowing me to be your mother," wrote Fergie. "You have always been the blood in my veins. From the time you were wee tots, you made my life complete. I look at how full of humility, laughter and joy you are in your hearts, and I marvel at you both. Now, in you as mothers, I see strength, courage and steadfastness, integrity and goodness, and the way you embrace every challenge and moment. It is an extraordinary feeling when your child becomes a mother."
She continued, "Suddenly my little girlies have their own little ones ... such a feeling to get used to. But if I do cry or tear up as you drive away, it is only because I am so proud of you. It has been just us for 33 years, but now you are creating your own families, and I couldn't be happier for you both and my magnificent sons-in-law, Jack and Edo."
Max Mumby/Indigo/Getty Images Princess Eugenie, Sarah Ferguson and Princess Beatrice
Fergie said that being a "young grandma" at 61 makes her "smile from my heart every day, because that is how it feels to be a granny" — and she can't wait to share the children's books she has written with her grandchildren, the "perfect new audience."
"You are resilient, calm and oh so kind, and your compassion and understanding of life give me more satisfaction than I can say and make me so deeply proud," she said. "I marvel at your cleverness in how you manage your lives. Nothing gives me more pleasure than watching you be incredible mothers."
Fergie also addressed how Princess Beatrice and Princess Eugenie experienced harsh criticism as part of their royal life in the public eye.
"You have both withstood cruelty in the face of cyberbullying, keyboard warriors and social media trolling," the Duchess of York wrote. "You have stood strong in the face of such adversity. Whatever faces you, still you remain in harmony with life."
Tim Graham Photo Library via Getty Images Sarah Ferguson, Princess Eugenie and Princess Beatrice
Fergie also shared the lesson that she hopes her daughters pass onto their own children.
"When your children walk on their own journeys, please teach them to be authentic to themselves, like I taught you," she said. "Tell them to always try to turn to joy — to see nature, hear the birds sing, feel the rain droplets that make trees smile. Believe in fairies and the magic of every day. Never give up on the road to smiles and rainbows, and remember the saying 'This too shall pass, like the clouds in the sky.'"
"I'm self-deprecating and British. But [one thing] is I'm a really good mom," she said.
"And I'm a good mom because, in growing up, when the girls used to say, 'Why can't we do that?'" she continued. "I would say, "Well, I've already made those mistakes. The world's press has written about my mistakes, so you don't need to make them now. So I've gone ahead of you to clear the way so that you can dream and grow and be who you are."